
TWR-K60N512 Tower Module User's Manual Page 8 of 18
SPI, I2C (w/ SMBUS support), UART (w/ ISO7816 and IrDA), CAN, I2S
SD Host Controller (SDHC)
GPIO with pin interrupt support, DMA request capability, digital glitch filtering
Capacitive touch sensing inputs (TSI)
Debug interfaces: JTAG, cJTAG, SWD
Trace: TPIO, FPB, DWT, ITM, ETM, ETB
2.2 Clocking
The Kinetis MCUs start up from an internal digitally controlled oscillator (DCO). Software can enable
one or two external oscillators if desired. The external oscillator for the Multipurpose Clock Generator
(MCG) module can range from 32.768 KHz up to a 32 MHz crystal or ceramic resonator. The external
oscillator for the Real Time Clock (RTC) module accepts a 32.768 kHz crystal.
The EXTAL pin of the main external oscillator can also be driven directly from an external clock source.
The TWR-K60N512 features a 50 MHz on-board clock oscillator as seen in sheet 4 of the schematics.
However, when the K60 Ethernet MAC is operating in RMII mode, synchronization of the MCU input
clock and the 50 MHz RMII transfer clock is important. In this mode, the MCU input clock must be kept
in phase with the 50 MHz clock supplied to the external PHY. Therefore, the TWR-K60N512 provides
the option (see description for J6 in Table 5) to select the clock input to the MCU from 1) the on-board
50MHz source or 2) an external clock from the CLKIN0 pin on the Primary Connector. When the K60 is
operating in Ethernet RMII mode, the Tower peripheral module implementing the RMII PHY device
should drive a 50 MHz clock on the CLKIN0 signal that is kept in phase with the clock supplied to the
RMII PHY. Refer to section 2.10 “Ethernet” for more information.
2.3 System Power
In stand-alone operation, the main power source for the TWR-K60N512 module is derived from the
5.0V input from either the USB mini-B connector, J13, or the debug header, J11, when a shunt is placed
on jumper J12. A low-dropout regulator provides a 3.3V supply from the 5.0V input voltage. Refer to
sheet 5 of the TWR-K60N512 schematics for more details.
When installed into a Tower System, the TWR-K60N512 can be powered from either an on-board
source or from another source in the assembled Tower System. If both the on-board and off-board
sources are available, the TWR-K60N512 will default to the off-board source.
The 3.3V power supplied to the MCU is routed through a jumper, J8. The jumper shunt can be removed
to allow for either 1) alternate MCU supply voltages to be injected or 2) the measurement of power
consumed by the MCU.
2.3.1 RTC VBAT
The Real Time Clock (RTC) module on the K60 has two modes of operation, system power-up and
system power-down. During system power-down, the RTC is powered from the backup power supply,
VBAT. The TWR-K60N512 provides a battery holder for a coin cell battery that can be used as the VBAT
supply. The holder can accept common 20mm diameter 3V lithium coin cell batteries (e.g. 2032,
2025). Refer to the description J9 in Table 5 “TWR-K60N512 Jumper Table” for more information.