STMicroelectronics STM32F427 User manual

September 2013 DocID023833 Rev 5 1/36
STM32F42xx and STM32F43xx
Errata sheet
STM32F427/437 and STM32F429/439 line limitations
Silicon identification
This errata sheet applies to the revision A and Y of STMicroelectronics STM32F427/437
and STM32F429/439 microcontroller lines.
The STM32F42xx and STM32F43xx devices featurean ARM®32-bit Cortex™-M4 core with
FPU, for which an errata notice is also available (see Section 1 for details).
The full list of part numbers is shown in Table 2. The products are identifiable as shown in
Table 1:
•by the revision code marked below the order code on the device package
•by the last three digits of the Internal order code printed on the box label
Table 1. Device identification(1)
1. The REV_ID bits in the DBGMCU_IDCODE register show the revision code of the device (see the RM0090
STM32F4xx reference manual for details on how to find the revision code).
Order code Revision code marked on device(2)
2. Refer to Appendix A: Revision code on device marking for details on how to identify the revision code and
the date code on the different packages.
STM32F427xx, STM32F429xx “A” and “Y”
STM32F437xx, STM32F439xx
Table 2. Device summary
Reference Part number
STM32F427xx STM32F427VG, STM32F427ZG, STM32F427IG, STM32F427VI, STM32F427ZI,
STM32F427II
STM32F437xx STM32F437VG, STM32F437ZG, STM32F437IG, STM32F437VI, STM32F437ZI,
STM32F437II
STM32F429xx STM32F429VG, STM32F429ZG, STM32F429IG, STM32F429VI, STM32F429ZI,
STM32F429II, STM32F429BG, STM32F429BI, STM32F429NI, STM32F429NG
STM32F439xx STM32F439VI, STM32F439VG, STM32F439ZG, STM32F439ZI, STM32F439IG,
STM32F439II, STM32F439BG, STM32F439BI, STM32F439NI, STM32F439NG
www.st.com

Contents STM32F42xx and STM32F43xx
2/36 DocID023833 Rev 5
Contents
1 ARM 32-bit Cortex-M4 with FPU limitations . . . . . . . . . . . . . . . . . . . . . . 7
1.1 Cortex-M4 interrupted loads to stack pointer can cause
erroneous behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 STM32F42xx and STM32F43xx silicon limitations . . . . . . . . . . . . . . . . . 8
2.1 System limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.1 Debugging Stop mode and system tick timer . . . . . . . . . . . . . . . . . . . . 10
2.1.2 Debugging Stop mode with WFE entry . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.3 Wakeup sequence from Standby mode when using more than
one wakeup source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.4 Full JTAG configuration without NJTRST pin cannot be used . . . . . . . . 11
2.1.5 MPU attribute to RTC and IWDG registers could be managed
incorrectly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.6 Delay after an RCC peripheral clock enabling . . . . . . . . . . . . . . . . . . . . 12
2.1.7 Internal noise impacting the ADC accuracy . . . . . . . . . . . . . . . . . . . . . . 12
2.1.8 Over-drive and Under-drive modes unavailability . . . . . . . . . . . . . . . . . 13
2.2 IWDG peripheral limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 RVU and PVU flags are not reset in STOP mode . . . . . . . . . . . . . . . . . 13
2.3 I2C peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3.1 SMBus standard not fully supported . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3.2 Start cannot be generated after a misplaced Stop . . . . . . . . . . . . . . . . . 14
2.3.3 Mismatch on the “Setup time for a repeated Start condition” timing
parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.4 Data valid time (tVD;DAT) violated without the OVR flag being set . . . . . 14
2.3.5 Both SDA and SCL maximum rise time (tr) violated when VDD_I2C bus
higher than ((VDD+0.3) / 0.7) V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4 I2S peripheral limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4.1 In I2S slave mode, WS level must be set by the external master
when enabling the I2S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5 USART peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.1 Idle frame is not detected if receiver clock speed is deviated . . . . . . . . 16
2.5.2 In full duplex mode, the Parity Error (PE) flag can be cleared by
writing to the data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.3 Parity Error (PE) flag is not set when receiving in Mute mode
using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.4 Break frame is transmitted regardless of nCTS input line status . . . . . . 17

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2.5.5 nRTS signal abnormally driven low after a protocol violation . . . . . . . . 17
2.6 OTG_FS peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.6.1 Data in RxFIFO is overwritten when all channels are disabled
simultaneously . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.6.2 OTG host blocks the receive channel when receiving IN packets and no
TxFIFO is configured . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.6.3 Host channel-halted interrupt not generated when the channel is
disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.6.4 Error in software-read OTG_FS_DCFG register values . . . . . . . . . . . . 18
2.7 Ethernet peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.7.1 Incorrect layer 3 (L3) checksum is inserted in transmitted IPv6 packets
without TCP, UDP or ICMP payloads . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.7.2 The Ethernet MAC processes invalid extension headers in the received
IPv6 frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.7.3 MAC stuck in the Idle state on receiving the TxFIFO flush command
exactly 1 clock cycle after a transmission completes . . . . . . . . . . . . . . . 19
2.7.4 Transmit frame data corruption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.7.5 Successive write operations to the same register might not be fully
taken into account . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.8 FMC peripheral limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.8.1 Dummy read cycles inserted when reading synchronous memories . . . 23
2.8.2 FMC synchronous mode and NWAIT signal disabled . . . . . . . . . . . . . . 23
2.8.3 Read access to a non-initialized FMC_SDRAM bank . . . . . . . . . . . . . . 23
2.8.4 Corruption of data read from the FMC . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.8.5 Interruption of CPU read burst access to an end of SDRAM row . . . . . 24
2.8.6 FMC NOR/PSRAM controller: asynchronous read access on bank 2 to 4
returns wrong data when bank 1 is in synchronous mode
(BURSTEN bit is set) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.8.7 FMC dynamic and static banks switching . . . . . . . . . . . . . . . . . . . . . . . 25
2.9 SDIO peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.9.1 SDIO HW flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.9.2 Wrong CCRCFAIL status after a response without CRC is received . . . 25
2.9.3 Data corruption in SDIO clock dephasing (NEGEDGE) mode . . . . . . . . 26
2.9.4 CE-ATA multiple write command and card busy signal management . . 26
2.9.5 No underrun detection with wrong data transmission . . . . . . . . . . . . . . 26
2.10 ADC peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.10.1 ADC sequencer modification during conversion . . . . . . . . . . . . . . . . . . 27
2.11 DAC peripheral limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.11.1 DMA underrun flag management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Contents STM32F42xx and STM32F43xx
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2.11.2 DMA request not automatically cleared by DMAEN=0 . . . . . . . . . . . . . 27
Appendix A Revision code on device marking . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

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STM32F42xx and STM32F43xx List of tables
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List of tables
Table 1. Device identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table 2. Device summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table 3. Cortex-M4 core limitations and impact on microcontroller behavior. . . . . . . . . . . . . . . . . . . 7
Table 4. Summary of silicon limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 5. Impacted registers and bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 6. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

List of figures STM32F42xx and STM32F43xx
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List of figures
Figure 1. TFBGA216 top package view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 2. WLCSP143 top package view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 3. LQFP208 top package view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 4. UFBGA176 top package view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 5. LQFP176 top package view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 6. LQFP144 top package view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 7. LQFP100 top package view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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STM32F42xx and STM32F43xx ARM 32-bit Cortex-M4 with FPU limitations
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1 ARM 32-bit Cortex-M4 with FPU limitations
An errata notice of the STM32F42xx and STM32F43xx core is available from the following
web address:
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0439b_errata_01/index.html.
All the described limitations are minor and related to the revision r0p1-v1 of the CortexM4
core. Table 3 summarizes these limitations and their implications on the behavior of
STM32F42xx and STM32F43xx devices.
1.1 Cortex-M4 interrupted loads to stack pointer can cause
erroneous behavior
Description
An interrupt occurring during the data-phase of a single word load to the stack pointer
(SP/R13) can cause an erroneous behavior of the device. In addition, returning from the
interrupt results in the load instruction being executed an additional time.
For all the instructions performing an update of the base register, the base register is
erroneously updated on each execution, resulting in the stack pointer being loaded from an
incorrect memory location.
The instructions affected by this limitation are the following:
•LDR SP, [Rn],#imm
•LDR SP, [Rn,#imm]!
•LDR SP, [Rn,#imm]
•LDR SP, [Rn]
•LDR SP, [Rn,Rm]
Workaround
As of today, no compiler generates these particular instructions. This limitation can only
occur with hand-written assembly code.
Both limitations can be solved by replacing the direct load to the stack pointer by an
intermediate load to a general-purpose register followed by a move to the stack pointer.
Example:
Replace LDR SP, [R0] by
LDR R2,[R0]
MOV SP,R2
Table 3. Cortex-M4 core limitations and impact on microcontroller behavior
ARM ID ARM
category ARM summary of errata Impact on STM32F42xx
and STM32F43xx
752419 Cat 2 Interrupted loads to SP can cause erroneous
behavior Minor

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2 STM32F42xx and STM32F43xx silicon limitations
Table 4 gives quick references to all documented limitations.
Legend for Table 4: A = workaround available; N = no workaround available; P = partial
workaround available, ‘-’ and grayed = fixed.
Table 4. Summary of silicon limitations
Links to silicon limitations Revision A Revision Y
Section 2.1: System
limitations
Section 2.1.1: Debugging Stop mode and system tick timer AA
Section 2.1.2: Debugging Stop mode with WFE entry AA
Section 2.1.3: Wakeup sequence from Standby mode
when using more than one wakeup source AA
Section 2.1.4: Full JTAG configuration without NJTRST pin
cannot be used AA
Section 2.1.5: MPU attribute to RTC and IWDG registers
could be managed incorrectly AA
Section 2.1.6: Delay after an RCC peripheral clock
enabling AA
Section 2.1.7: Internal noise impacting the ADC accuracy AA
Section 2.1.8: Over-drive and Under-drive modes
unavailability N-
Section 2.2: IWDG
peripheral limitation Section 2.2.1: RVU and PVU flags are not reset in STOP mode AA
Section 2.3: I2C peripheral
limitations
Section 2.3.1: SMBus standard not fully supported AA
Section 2.3.2: Start cannot be generated after a misplaced
Stop AA
Section 2.3.3: Mismatch on the “Setup time for a repeated
Start condition” timing parameter AA
Section 2.3.4: Data valid time (tVD;DAT) violated without
the OVR flag being set AA
Section 2.3.5: Both SDA and SCL maximum rise time (tr)
violated when VDD_I2C bus higher than ((VDD+0.3) /
0.7) V AA
Section 2.4: I2S peripheral
limitation Section 2.4.1: In I2S slave mode, WS level must be set by the external master when enabling the I2S AA

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Section 2.5: USART
peripheral limitations
Section 2.5.1: Idle frame is not detected if receiver clock
speed is deviated NN
Section 2.5.2: In full duplex mode, the Parity Error (PE) flag
can be cleared by writing to the data register AA
Section 2.5.3: Parity Error (PE) flag is not set when
receiving in Mute mode using address mark detection NN
Section 2.5.4: Break frame is transmitted regardless of
nCTS input line status NN
Section 2.5.5: nRTS signal abnormally driven low after a
protocol violation AA
Section 2.6: OTG_FS
peripheral limitations
Section 2.6.1: Data in RxFIFO is overwritten when all
channels are disabled simultaneously AA
Section 2.6.2: OTG host blocks the receive channel when
receiving IN packets and no TxFIFO is configured AA
Section 2.6.3: Host channel-halted interrupt not generated
when the channel is disabled AA
Section 2.6.4: Error in software-read OTG_FS_DCFG
register values AA
Section 2.7: Ethernet
peripheral limitations
Section 2.7.1: Incorrect layer 3 (L3) checksum is inserted
in transmitted IPv6 packets without TCP, UDP or ICMP
payloads AA
Section 2.7.2: The Ethernet MAC processes invalid
extension headers in the received IPv6 frames NN
Section 2.7.3: MAC stuck in the Idle state on receiving the
TxFIFO flush command exactly 1 clock cycle after a
transmission completes AA
Section 2.7.4: Transmit frame data corruption AA
Section 2.7.5: Successive write operations to the same
register might not be fully taken into account AA
Section 2.8:FMCperipheral
limitation
Section 2.8.1: Dummy read cycles inserted when reading
synchronous memories NN
Section 2.8.2: FMC synchronous mode and NWAIT signal
disabled AA
Section 2.8.3: Read access to a non-initialized
FMC_SDRAM bank PP
Section 2.8.4: Corruption of data read from the FMC A-
Section 2.8.5: Interruption of CPU read burst access to an
end of SDRAM row AA
Section 2.8.6: FMC NOR/PSRAM controller: asynchronous
read access on bank 2 to 4 returns wrong data when bank
1 is in synchronous mode (BURSTEN bit is set) AA
Section 2.8.7: FMC dynamic and static banks switching AA
Table 4. Summary of silicon limitations (continued)
Links to silicon limitations Revision A Revision Y

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2.1 System limitations
2.1.1 Debugging Stop mode and system tick timer
Description
If the system tick timer interrupt is enabled during the Stop mode debug (DBG_STOP bit set
in the DBGMCU_CR register), it will wake up the system from Stop mode.
Workaround
To debug the Stop mode, disable the system tick timer interrupt.
2.1.2 Debugging Stop mode with WFE entry
Description
When the Stop debug mode is enabled (DBG_STOP bit set in the DBGMCU_CR register),
this allows software debugging during Stop mode.
However, if the application software uses the WFE instruction to enter Stop mode, after
wakeup some instructions could be missed if the WFE is followed by sequential instructions.
This affects only Stop debug mode with WFE entry.
Workaround
To debug Stop mode with WFE entry, the WFE instruction must be inside a dedicated
function with 1 instruction (NOP) between the execution of the WFE and the Bx LR.
Example:
__asm void _WFE(void) {
WFE
Section 2.9: SDIO
peripheral limitations
Section 2.9.1: SDIO HW flow control NN
Section 2.9.2: Wrong CCRCFAIL status after a response
without CRC is received AA
Section 2.9.3: Data corruption in SDIO clock dephasing
(NEGEDGE) mode NN
Section 2.9.4: CE-ATA multiple write command and card
busy signal management AA
Section 2.9.5: No underrun detection with wrong data
transmission AA
Section 2.10: ADC
peripheral limitations Section 2.10.1: ADC sequencer modification during conversion AA
Section 2.11: DAC
peripheral limitations
Section 2.11.1: DMA underrun flag management AA
Section 2.11.2: DMA request not automatically cleared by
DMAEN=0 AA
Table 4. Summary of silicon limitations (continued)
Links to silicon limitations Revision A Revision Y

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NOP
BX lr }
2.1.3 Wakeup sequence from Standby mode when using more than
one wakeup source
Description
The various wakeup sources are logically OR-ed in front of the rising-edge detector which
generates the wakeup flag (WUF). The WUF needs to be cleared prior to Standby mode
entry, otherwise the MCU wakes up immediately.
If one of the configured wakeup sources is kept high during the clearing of the WUF (by
setting the CWUF bit), it may mask further wakeup events on the input of the edge detector.
As a consequence, the MCU might not be able to wake up from Standby mode.
Workaround
To avoid this problem, the following sequence should be applied before entering
Standby mode:
•Disable all used wakeup sources,
•Clear all related wakeup flags,
•Re-enable all used wakeup sources,
•Enter Standby mode
Note: Be aware that, when applying this workaround, if one of the wakeup sources is still kept
high, the MCU enters Standby mode but then it wakes up immediately generating a power
reset.
2.1.4 Full JTAG configuration without NJTRST pin cannot be used
Description
When using the JTAG debug port in debug mode, the connection with the debugger is lost if
the NJTRST pin (PB4) is used as a GPIO. Only the 4-wire JTAG port configuration is
impacted.
Workaround
Use the SWD debug port instead of the full 4-wire JTAG port.

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2.1.5 MPU attribute to RTC and IWDG registers could be managed
incorrectly
Description
If the MPU is used and the non bufferable attribute is set to the RTC or IWDG memory map
region, the CPU access to the RTC or IWDG registers could be treated as bufferable,
provided that there is no APB prescaler configured (AHB/APB prescaler is equal to 1).
Workaround
If the non bufferable attribute is required for these registers, the software could perform a
read after the write to guaranty the completion of the write access.
2.1.6 Delay after an RCC peripheral clock enabling
Description
A delay between an RCC peripheral clock enable and the effective peripheral enabling
should be taken into account in order to manage the peripheral read/write to registers.
This delay depends on the peripheral’s mapping:
•If the peripheral is mapped on AHB: the delay should be equal to 2 AHB cycles.
•If the peripheral is mapped on APB: the delay should be equal to 1 + (AHB/APB
prescaler) cycles.
Workarounds
1. Use the DSB instruction to stall the Cortex-M CPU pipeline until the instruction is
completed.
2. Insert “n” NOPs between the RCC enable bit write and the peripheral register writes
(n = 2 for AHB peripherals, n = 1 + AHB/APB prescaler in case of APB peripherals).
2.1.7 Internal noise impacting the ADC accuracy
Description
An internal noise generated on VDD supplies and propagated internally may impact the ADC
accuracy.
This noise is always active whatever the power mode of the MCU (RUN or Sleep).
Workarounds
To adapt the accuracy level to the application requirements, set one of the following options:
•Option1
Set the ADCDC1 bit in the PWR_CR register.
•Option2
Set the corresponding ADCxDC2 bit in the SYSCFG_PMC register.
Only one option can be set at a time.
For more details on option 1 and option2 mechanisms, refer to AN4073.

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2.1.8 Over-drive and Under-drive modes unavailability
Description
The Over-drive and Under-drive modes are not available on revision A devices.
Workaround
None.
This limitation is fixed in silicon revision Y.
2.2 IWDG peripheral limitation
2.2.1 RVU and PVU flags are not reset in STOP mode
Description
The RVU and PVU flags of the IWDG_SR register are set by hardware after a write access
to the IWDG_RLR and the IWDG_PR registers, respectively. If the Stop mode is entered
immediately after the write access, the RVU and PVU flags are not reset by hardware.
Before performing a second write operation to the IWDG_RLR or the IWDG_PR register,
the application software must wait for the RVU or PVU flag to be reset. However, since the
RVU/PVU bit is not reset after exiting the Stop mode, the software goes into an infinite loop
and the independent watchdog (IWDG) generates a reset after the programmed timeout
period.
Workaround
Wait until the RVU or PVU flag of the IWDG_SR register is reset before entering the Stop
mode.
2.3 I2C peripheral limitations
2.3.1 SMBus standard not fully supported
Description
The I2C peripheral is not fully compliant with the SMBus v2.0 standard since It does not
support the capability to NACK an invalid byte/command.
Workarounds
A higher-level mechanism should be used to verify that a write operation is being performed
correctly at the target device, such as:
1. Using the SMBAL pin if supported by the host
2. the alert response address (ARA) protocol
3. the Host notify protocol

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2.3.2 Start cannot be generated after a misplaced Stop
Description
If a master generates a misplaced Stop on the bus (bus error), the peripheral cannot
generate a Start anymore.
Workaround
In the I²C standard, it is allowed to send a Stop only at the end of the full byte (8 bits +
acknowledge), so this scenario is not allowed. Other derived protocols like CBUS allow it,
but they are not supported by the I²C peripheral.
A software workaround consists in asserting the software reset using the SWRST bit in the
I2C_CR1 control register.
2.3.3 Mismatch on the “Setup time for a repeated Start condition” timing
parameter
Description
In case of a repeated Start, the “Setup time for a repeated Start condition” (named Tsu;sta in
the I²C specification) can be slightly violated when the I²C operates in Master Standard
mode at a frequency between 88 kHz and 100 kHz.
The limitation can occur only in the following configuration:
•in Master mode
•in Standard mode at a frequency between 88 kHz and 100 kHz (no limitation in Fast-
mode)
•SCL rise time:
– If the slave does not stretch the clock and the SCL rise time is more than 300 ns (if
the SCL rise time is less than 300 ns, the limitation cannot occur)
– If the slave stretches the clock
The setup time can be violated independently of the APB peripheral frequency.
Workaround
Reduce the frequency down to 88 kHz or use the I²C Fast-mode, if supported by the slave.
2.3.4 Data valid time (tVD;DAT) violated without the OVR flag being set
Description
The data valid time (tVD;DAT, tVD;ACK) described by the I²C standard can be violated (as well
as the maximum data hold time of the current data (tHD;DAT)) under the conditions described
below. This violation cannot be detected because the OVR flag is not set (no transmit buffer
underrun is detected).
This limitation can occur only under the following conditions:
•in Slave transmit mode
•with clock stretching disabled (NOSTRETCH=1)
•if the software is late to write the DR data register, but not late enough to set the OVR
flag (the data register is written before)

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Workaround
If the master device allows it, use the clock stretching mechanism by programming the bit
NOSTRETCH=0 in the I2C_CR1 register.
If the master device does not allow it, ensure that the software is fast enough when polling
the TXE or ADDR flag to immediately write to the DR data register. For instance, use an
interrupt on the TXE or ADDR flag and boost its priority to the higher level.
2.3.5 Both SDA and SCL maximum rise time (tr) violated when VDD_I2C bus
higher than ((VDD+0.3) / 0.7) V
Description
When an external legacy I2C bus voltage (VDD_I2C) is set to 5 V while the MCU is powered
from VDD, the internal 5-Volt tolerant circuitry is activated as soon the input voltage (VIN)
reaches the VDD + diode threshold level. An additional internal large capacitance then
prevents the external pull-up resistor (RP) from rising the SDA and SCL signals within the
maximum timing (tr) which is 300 ns in fast mode and 1000 ns in Standard mode.
The rise time (tr) is measured from VIL and VIH with levels set at 0.3VDD_I2C and
0.7VDD_I2C.
Workaround
The external VDD_I2C bus voltage should be limited to a maximum value of
((VDD+0.3) / 0.7) V. As a result, when the MCU is powered from VDD=3.3 V, VDD_I2C
should not exceed 5.14 V to be compliant with I2C specifications.
2.4 I2S peripheral limitation
2.4.1 In I2S slave mode, WS level must be set by the external master
when enabling the I2S
Description
In slave mode, the WS signal level is used only to start the communication. If the I2S (in
slave mode) is enabled while the master is already sending the clock and the WS signal
level is low (for I2S protocol) or is high (for the LSB or MSB-justified mode), the slave starts
communicating data immediately. In this case, the master and slave will be desynchronized
throughout the whole communication.
Workaround
The I2S peripheral must be enabled when the external master sets the WS line at:
•High level when the I2S protocol is selected.
•Low level when the LSB or MSB-justified mode is selected.

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2.5 USART peripheral limitations
2.5.1 Idle frame is not detected if receiver clock speed is deviated
Description
If the USART receives an idle frame followed by a character, and the clock of the transmitter
device is faster than the USART receiver clock, the USART receive signal falls too early
when receiving the character start bit, with the result that the idle frame is not detected
(IDLE flag is not set).
Workaround
None.
2.5.2 In full duplex mode, the Parity Error (PE) flag can be cleared by
writing to the data register
Description
In full duplex mode, when the Parity Error flag is set by the receiver at the end of a
reception, it may be cleared while transmitting by reading the USART_SR register to check
the TXE or TC flags and writing data to the data register.
Consequently, the software receiver can read the PE flag as '0' even if a parity error
occurred.
Workaround
The Parity Error flag should be checked after the end of reception and before transmission.
2.5.3 Parity Error (PE) flag is not set when receiving in Mute mode
using address mark detection
Description
The USART receiver is in Mute mode and is configured to exit the Mute mode using the
address mark detection. When the USART receiver recognizes a valid address with a parity
error, it exits the Mute mode without setting the Parity Error flag.
Workaround
None.

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2.5.4 Break frame is transmitted regardless of nCTS input line status
Description
When CTS hardware flow control is enabled (CTSE = 1) and the Send Break bit (SBK) is
set, the transmitter sends a break frame at the end of the current transmission regardless of
nCTS input line status.
Consequently, if an external receiver device is not ready to accept a frame, the transmitted
break frame is lost.
Workaround
None.
2.5.5 nRTS signal abnormally driven low after a protocol violation
Description
When RTS hardware flow control is enabled, the nRTS signal goes high when data is
received. If this data was not read and new data is sent to the USART (protocol violation),
the nRTS signal goes back to low level at the end of this new data.
Consequently, the sender gets the wrong information that the USART is ready to receive
further data.
On USART side, an overrun is detected, which indicates that data has been lost.
Workaround
Workarounds are required only if the other USART device violates the communication
protocol, which is not the case in most applications.
Two workarounds can be used:
•After data reception and before reading the data in the data register, the software takes
over the control of the nRTS signal as a GPIO and holds it high as long as needed. If
the USART device is not ready, the software holds the nRTS pin high, and releases it
when the device is ready to receive new data.
•The time required by the software to read the received data must always be lower than
the duration of the second data reception. For example, this can be ensured by treating
all the receptions by DMA mode.
2.6 OTG_FS peripheral limitations
2.6.1 Data in RxFIFO is overwritten when all channels are disabled
simultaneously
Description
If the available RxFIFO is just large enough to host 1 packet + its data status, and is
currently occupied by the last received data + its status and, at the same time, the
application requests that more IN channels be disabled, the OTG_FS peripheral does not
first check for available space before inserting the disabled status of the IN channels. It just
inserts them by overwriting the existing data payload.

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Workaround
Use one of the following recommendations:
1. Configure the RxFIFO to host a minimum of 2 × MPSIZ + 2 × data status entries.
2. The application has to check the RXFLVL bit (RxFIFO non-empty) in the
OTG_FS_GINTSTS register before disabling each IN channel. If this bit is not set, then
the application can disable an IN channel at a time. Each time the application disables
an IN channel, however, it first has to check that the RXFLVL bit = 0 condition is true.
2.6.2 OTG host blocks the receive channel when receiving IN packets and no
TxFIFO is configured
Description
When receiving data, the OTG_FS core erroneously checks for available TxFIFO space
when it should only check for RxFIFO space. If the OTG_FS core cannot see any space
allocated for data transmission, it blocks the reception channel and no data is received.
Workaround
Set at least one TxFIFO equal to the maximum packet size. In this way, the host application,
which intends to supports only IN traffic, also has to allocate some space for the TxFIFO.
Since a USB host is expected to support any kind of connected endpoint, it is good practice
to always configure enough TxFIFO space for OUT endpoints.
2.6.3 Host channel-halted interrupt not generated when the channel is
disabled
Description
When the application enables, then immediately disables the host channel before the
OTG_FS host has had time to begin the transfer sequence, the OTG_FS core, as a host,
does not generate a channel-halted interrupt. The OTG_FS core continues to operate
normally.
Workaround
Do not disable the host channel immediately after enabling it.
2.6.4 Error in software-read OTG_FS_DCFG register values
Description
When the application writes to the DAD and PFIVL bitfields in the OTG_FS_DCFG register,
and then reads the newly written bitfield values, the read values may not be correct.
The values written by the application, however, are correctly retained by the core, and the
normal operation of the device is not affected.
Workaround
Do not read from the OTG_FS_DCFG register’s DAD and PFIVL bitfields just after
programming them.

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2.7 Ethernet peripheral limitations
2.7.1 Incorrect layer 3 (L3) checksum is inserted in transmitted IPv6 packets
without TCP, UDP or ICMP payloads
Description
The application provides the per-frame control to instruct the MAC to insert the L3
checksums for TCP, UDP and ICMP packets. When automatic checksum insertion is
enabled and the input packet is an IPv6 packet without the TCP, UDP or ICMP payload, then
the MAC may incorrectly insert a checksum into the packet. For IPv6 packets without a TCP,
UDP or ICMP payload, the MAC core considers the next header (NH) field as the extension
header and continues to parse the extension header. Sometimes, the payload data in such
packets matches the NH field for TCP, UDP or ICMP and, as a result, the MAC core inserts
a checksum.
Workaround
When the IPv6 packets have a TCP, UDP or ICMP payload, enable checksum insertion for
transmit frames, or bypass checksum insertion by using the CIC (checksum insertion
control) bits in TDES0 (bits 23:22).
2.7.2 The Ethernet MAC processes invalid extension headers in the received
IPv6 frames
Description
In IPv6 frames, there can be zero or some extension headers preceding the actual IP
payload. The Ethernet MAC processes the following extension headers defined in the IPv6
protocol: Hop-by-Hop Options header, Routing header and Destination Options header.
All extension headers, except the Hop-by-Hop extension header, can be present multiple
times and in any order before the actual IP payload. The Hop-by-Hop extension header, if
present, has to come immediately after the IPv6’s main header.
The Ethernet MAC processes all (valid or invalid) extension headers including the Hop-by-
Hop extension headers that are present after the first extension header. For this reason, the
GMAC core will accept IPv6 frames with invalid Hop-by-Hop extension headers. As a
consequence, it will accept any IP payload as valid IPv6 frames with TCP, UDP or ICMP
payload, and then incorrectly update the Receive status of the corresponding frame.
Workaround
None.
2.7.3 MAC stuck in the Idle state on receiving the TxFIFO flush command
exactly 1 clock cycle after a transmission completes
Description
When the software issues a TxFIFO flush command, the transfer of frame data stops (even
in the middle of a frame transfer). The TxFIFO read controller goes into the Idle state
(TFRS=00 in ETH_MACDBGR) and then resumes its normal operation.

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However, if the TxFIFO read controller receives the TxFIFO flush command exactly one
clock cycle after receiving the status from the MAC, the controller remains stuck in the Idle
state and stops transmitting frames from the TxFIFO. The system can recover from this
state only with a reset (e.g. a soft reset).
Workaround
Do not use the TxFIFO flush feature.
If TXFIFO flush is really needed, wait until the TxFIFO is empty prior to using the TxFIFO
flush command.
2.7.4 Transmit frame data corruption
Frame data corrupted when the TxFIFO is repeatedly transitioning from non-empty to empty
and then back to non-empty.
Description
Frame data may get corrupted when the TxFIFO is repeatedly transitioning from non-empty
to empty for a very short period, and then from empty to non-empty, without causing an
underflow.
This transitioning from non-empty to empty and back to non-empty happens when the rate
at which the data is being written to the TxFIFO is almost equal to or a little less than the
rate at which the data is being read.
This corruption cannot be detected by the receiver when the CRC is inserted by the MAC,
as the corrupted data is used for the CRC computation.
Workaround
Use the Store-and-Forward mode: TSF=1 (bit 21 in ETH_DMAOMR). In this mode, the data
is transmitted only when the whole packet is available in the TxFIFO.
2.7.5 Successive write operations to the same register might not be fully
taken into account
Description
A write to a register might not be fully taken into account if a previous write to the same
register is performed within a time period of four TX_CLK/RX_CLK clock cycles. When this
error occurs, reading the register returns the most recently written value, but the Ethernet
MAC continues to operate as if the latest write operation never occurred.
See Table 5: Impacted registers and bits for the registers and bits impacted by this limitation.