Freescale Semiconductor K20D72M User manual

Freescale Semiconductor Inc.
TWR-K20D72M
User Manual
Rev. 1.1

TWR-K20D72M User’s Manual Page 2 of 17
Contents
1 TWR-K20D72M Overview ......................................................................................................................4
1.1 Features..................................................................................................................................................................................4
1.2 Getting started .....................................................................................................................................................................5
1.3 Reference Documents.......................................................................................................................................................5
2 Hardware Description.............................................................................................................................5
2.1 K20D72M Microcontroller..............................................................................................................................................6
2.2 Clocking ..................................................................................................................................................................................7
2.3 System Power.......................................................................................................................................................................7
2.3.1 Board Power Select ...........................................................................................................................................................................7
2.3.2 RTC VBAT ..............................................................................................................................................................................................7
2.4 Debug Interface ...................................................................................................................................................................8
2.4.1 OSJTAG ....................................................................................................................................................................................................8
2.4.2 Cortex Debug Connector .................................................................................................................................................................8
2.5 USB Interface........................................................................................................................................................................9
2.6 Infrared Port.........................................................................................................................................................................9
2.7 External Bus Interface – FlexBus..................................................................................................................................9
2.8 Accelerometer......................................................................................................................................................................9
2.9 Potentiometer, Pushbuttons, LEDs .............................................................................................................................9
2.10 General Purpose Tower Plug-in (TWRPI) Socket............................................................................................ 10
2.11 Touch Interface.............................................................................................................................................................. 10
2.12 Microphone and buzzer.............................................................................................................................................. 11
3 Jumper Table ........................................................................................................................................... 12
4 Input/Output Connectors and Pin Usage Table........................................................................... 13
5 Elevator Connections ............................................................................................................................ 15

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List of Figures
Figure 1. Front side of TWR-K20D72M module.......................................................................................... 4
Figure 2. Back side of TWR-K20D72M module........................................................................................... 5
Figure 3.TWR-K20D72M Block Diagram .................................................................................................... 6
Figure 4. Infrared Port Implementation ..................................................................................................... 9
List of Tables
Table 1. Cortex Debug Connector Pinout................................................................................................... 8
Table 2. TWRPI Socket Pin Description..................................................................................................... 10
Table 3. Touch TWRPI Pin Description ..................................................................................................... 11
Table 4. TWR-K20D72M Jumper Table..................................................................................................... 12
Table 5. I/O Connectors and Pin Usage Table .......................................................................................... 13
Table 6. TWR-K20D72M Primary Connector Pinout................................................................................. 15
Revision History
Revision Date Changes
0.1 March 15, 2011 Initial Release

TWR-K20D72M User’s Manual Page 4 of 17
1TWR-K20D72M Overview
The K20D72M Tower MCU Module (TWR-K20D72M) is a low-cost evaluation, demonstration and
development board, which features the Kinetis K20 72MHz low-power microcontroller. These devices
are based on the ARM® Cortex™-M4 architecture with USB 2.0 full-speed OTG controller. The TWR-
K20D72M microcontroller module can operate in stand-alone mode or as part of the Freescale Tower
System, a modular development platform that enables rapid prototyping and tool re-use through
reconfigurable hardware. Take your design to the next level and begin constructing your Tower
System today by visiting www.freescale.com/tower for additional Tower System microcontroller
modules and compatible peripherals.
1.1 Features
The following list summarizes the features of the K20D72M Tower MCU boards:
•Tower compatible processor board
•S08JM60 based Open Source BDM (OSBDM) circuit
•Four (4) user-controlled status LEDs
•Two (2) Capacitive Touch Pads and two (2) mechanical push buttons
•Socket for Capacitive Touch Pad daughter board (Touch TWRPI)
•Socket for Tower Plug-in (TWRPI, e.g. sensor board)
•Standalone USB host and device function
•Microphone and buzzer
•Potentiometer
•MMA8451Q three-axis accelerometer
•Battery holder for 20mm lithium battery (e.g. 2032, 2025)
•Board power select with 3.3V or 1.8V MCU operation
Figure 1. Front side of TWR-K20D72M module

TWR-K20D72M User’s Manual Page 5 of 17
Figure 2. Back side of TWR-K20D72M module
1.2 Getting started
Follow the Quick Start Guide found printed in the TWR-K20D72M box or the interactive DVD for the list
of recommended steps for getting started. There are also lab walk-through guides available on the
tool support page for the TWR-K20D72M: http://www.freescale.com/TWR-K20D72M.
1.3 Reference Documents
The documents listed below should be referenced for more information on the Kinetis family, Tower
System and the MCU modules. These can be found in the documentation section
of http://www.freescale.com/TWR-K20D72M or http://www.freescale.com/kinetis.
•TWR-K20D72M Quick Start Guide
•TWR-K20D72M Schematics
•K20 Family Product Brief
•K20 Family Reference Manual
•Kinetis Quick Reference User Guide (KQRUG)
2Hardware Description
The TWR-K20D72M is a Tower System module featuring the MK20DX256VLL7 – an ARM® Cortex-M4™
based microcontroller with USB 2.0 full-speed OTG controllers in a 100LQFP package with a maximum
core operating frequency of 72MHz. It is intended for use in the Freescale Tower System but can
operate stand-alone. An on-board debug circuit, OSJTAG, provides a JTAG debug interface and a
power supply input through a single USB mini-AB connector. Figure 3 shows a block diagram for the
TWR-K20D72M.The following sections describe the hardware in more detail.

TWR-K20D72M User’s Manual Page 6 of 17
OSJTAG
JTAG, Power, SCI K20D72M
100 LQFP
(socket-IC
footprint)
USB
Mini-AB
Tower Elevator Expansion Connectors
I
2
S, SPI, I
2
C, USB, ADC, DAC, FTM, UARTs, Flexbus
8 MHz XTAL
SCI
Freescale Silicon External Connectors Interface Circuits Power
MMA8451Q
Infrared Port
IR Output
I
2
C
20-Pin
Header
Comparator
GPIO / Interrupts
ADC
Reset
LED
5V
32.768 KHz XTAL
3.3V
5.0V
Tower Plug-in
(TWRPI)
Sensor Socket
SPI, I
2
C, ADC, GPIO
Tower Plug-in
(TWRPI)
Touch
TSI, GPIO Capacitive
Touch
Pads
LED
LED
LED
Microphone/
amplifier
ADC
JTAG
USB Device/host
Micro
USB
VBAT (RTC)
General purpose
Tower Plug-in
(TWRPI)
3.3V
Regulator
1.8V
Regulator
Battery holder
Buzzer FTM
Figure 3: TWR-K20D72M Block Diagram
2.1 K20D72M Microcontroller
The TWR-K20D72M module features the MK20DX256VLL7.The Kinetis K20 microcontroller family is
part of the Kinetis portfolio of devices built around an ARM® Cortex-M4™ core. Refer to the K20
Family Product Brief and the K20 Family Reference Manual for comprehensive information on the
MK20DX256VLL7 device. MK20DX256VLL7key features:
•32-bit ARM Cortex-M4 core with DSP instructions
•72MHz maximum core operating frequency
•100LQFP, 14mm x 14mm, 0.5mm pitch package
•1.71V – 3.6V operating voltage input range
•256 Kbytes of program flash, 64 Kbytes of static RAM
•External bus interface
•Power management controller with 10 different power modes
•Multi-purpose clock generator with PLL and FLL operation modes
•16-bit SAR ADC, 12-bit DAC
•High-speed analog comparator with 6-bit DAC

TWR-K20D72M User’s Manual Page 7 of 17
•Programmable voltage reference
•USB full-speed/low-speed OTG/Host/Device controller with device charge detect
•SPI, I2C (w/ SMBUS support), UART (w/ ISO7816 and IrDA), CAN, I2S
•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
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.
Two crystals are provided on board for clocking the K20D72M device: 8 MHz crystal as main oscillator
to clock MCG module and 32.768 kHz crystal for clocking RTC module.
2.3 System Power
In standalone operation, the main power source for the TWR-K20D72M is derived from the 5.0V input
from either the USB mini-B connector, J14 or the debugger header, J11, when a shunt is placed on
jumper J10. On board low-dropout regulator provides either 3.3V or 1.8V supply from the 5.0V input
voltage based on jumper settings on J17, refer to sheet 5 of the TWR-K20D72M schematic for details.
When installed into a Tower System, the TWR-K20D72M 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-K20D72M will default to the off-board source.
The 3.3V or 1.8V power supplied to the MCU is routed through a jumper, J6. 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 Board Power Select
TWR-K20D72M board include on board regulators for both 3.3V and 1.8V output and add jumper J17
to select which one to use as board power and CPU power. This allows MCU operation under 1.8V
power supply.
2.3.2 RTC VBAT
The real time clock (RTC) module on the K20D72M 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-K20D72M provides a battery holder for a coin cell battery that can be used as the

TWR-K20D72M User’s Manual Page 8 of 17
VBAT supply. The holder can accept common 20mm diameter 3V lithium coin cell batteries (e.g. 2032,
2025). Refer to the description J13 in Table 4 “TWR-K20D72M Jumper Table” for more information.
2.4 Debug Interface
There are two debug interface options provided: the on-board OSJTAG circuit and an external Cortex
Debug connector.
2.4.1 OSJTAG
An on-board, MC9S08JM60 based Open Source BDM (OSBDM) circuit provides a debug interface to the
K20D72M. A standard USB A male to Mini-B male cable (provided) can be used for debugging via the
USB connector, J14. The OSJTAG interface also provides a USB to serial bridge. Drivers for the OSJTAG
interface are provided in the P&E Micro Kinetis Tower Toolkit (available on the included DVD).
2.4.2 Cortex Debug Connector
The Cortex Debug connector is a 20-pin (0.05") connector providing access to the SWD, SWV, JTAG,
cJTAG, EzPort signals available on the K20 device. The pinout and K20 pin connections to the debug
connector, J11, is shown in Table 1.
Table 1. Cortex Debug Connector Pinout
Pin Function TWR-K20D72M connection
1 VTref MCU supply (MCU_PWR)
2 TMS/SWDIO PTA3/UART0_RTS_b/FTM0_CH0/JTAG_MS/SWD_DIO
3 GND GND
4 TCK/SWCLK PTA0/UART0_CTS_b/FTM0_CH5/JTAG_CLK/SWD_CLK/EZP_CLK
5 GND GND
6 TDO/SWO PTA2/UART0_TX/FTM0_CH7/JTAG_DO/TRACE_SWO/EZP_DO
7 Key -
8 TDI PTA1/UART0_TX/FTM0_CH6/JTAG_DI/EZP_DI
9 GNDDetect PTA4/FTM0_CH1/MS/NMI_b/EZP_CS_b
10 nReset RESET_b
11 Target Power 5V supply (via J10)
12
-
-
13 Target Power 5V supply (via J10)
14 - -
15 GND GND
16 - -
17 GND GND
18 - -
19 GND GND
20 - -

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Note:there are no ETM signals on K20D72M, so the associated signals on Cortex Debugger connector
is left empty.
2.5 USB Interface
TWR-K20D72M board allows using USB as host or device in standalone mode or with connection to
TWR-SER board in a complete tower kit. Jumper J16 can be used to select which USB VBUS signal from
USB connector to connect with the MCU VREGIN input pin. When using in standalone mode, short 5-6
on J16 and connect USB with on board Micro-USB connector J19, when using with TWR-SER board in
complete tower kit, short 6-8 on J16 and connect USB with Mini-AB connector J14 on TWR-SER board.
Refer to description on J16 in Table 4 “TWR-K20D72M Jumper Table” for more information.
2.6 Infrared Port
An infrared transmit and receive interface is implemented as shown in Figure 4 below. The CMT_IRO
pin directly drives an infrared diode. The receiver uses an infrared phototransistor connected to an on-
chip analog comparator through a low-pass filter.
Figure 4: Infrared Port Implementation
2.7 External Bus Interface – FlexBus
The K20 device features a multi-function external bus interface called the FlexBus interface controller,
capable of interfacing to slave-only devices. The FlexBus interface is not used directly on the TWR-
K20D72M.Instead, a subset of the FlexBus is connected to the Primary Connector so that the external
bus can access devices on Tower peripheral modules. Refer to Table 6 “TWR-K20D72M Primary
Connector Pinout“and sheet 8 of the TWR-K20D72M schematics for more details.
2.8 Accelerometer
An MMA8451Q digital accelerometer is connected to the K20 MCU through an I2C interface and a
GPIO/IRQ signal. Refer to Table 5 “I/O Connectors and Pin Usage Table” for connection details.
2.9 Potentiometer, Pushbuttons, LEDs
The TWR-K20D72M features two pushbutton switches connected to GPIO/interrupt signals, one
pushbutton connected to the master reset signal, two capacitive touch pad electrodes, four user-

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controllable LEDs, and a potentiometer connected to an ADC input signal. Refer to Table 5 “I/O
Connectors and Pin Usage Table” for information about which port pins is connected to these features.
2.10 General Purpose Tower Plug-in (TWRPI) Socket
The TWR-K20D72M features a socket that can accept a variety of different Tower Plug-in modules
featuring sensors, RF transceivers, and more. The General Purpose TWRPI socket provides access to
I2C, SPI, IRQs, GPIOs, timers, analog conversion signals, TWRPI ID signals, reset, and voltage supplies.
The pinout for the TWRPI Socket is defined in Table 2.
Table 2. TWRPI Socket Pin Description
Left-side 2x10 Connector Right-side 2x10 Connector
Pin Description
1 5V VCC
2 3.3 V VCC
3 GND
4 3.3V VDDA
5 VSS (Analog GND)
6 VSS (Analog GND)
7 VSS (Analog GND)
8
ADC: Analog 0
9 ADC: Analog 1
10 VSS (Analog GND)
11 VSS (Analog GND)
12 ADC: Analog 2
13 VSS (Analog GND)
14 VSS (Analog GND)
15 GND
16 GND
17 ADC: TWRPI ID 0
18 ADC: TWRPI ID 1
19 GND
20 Reset
Pin Description
1 GND
2 GND
3 I2C: SCL
4 I2C: SDA
5 GND
6 GND
7 GND
8
GND
9 SPI: MISO
10 SPI: MOSI
11 SPI: SS
12 SPI: CLK
13 GND
14 GND
15 GPIO: GPIO0/IRQ
16 GPIO: GPIO1/IRQ
17 GPIO: GPIO2/UART0_RX
18 GPIO: GPIO3/ UART0_TX
19 GPIO: GPIO4/ UART0_CTS
20 GPIO: GPIO5/ UART0_RTS
2.11 Touch Interface
The touch sensing input (TSI) module of the Kinetis MCUs provides capacitive touch sensing detection
with high sensitivity and enhanced robustness. Each TSI pin implements the capacitive measurement
of an electrode.
The TWR-K20D72M provides two methods for evaluating the TSI module. There are two individual
electrodes on-board the TWR-K20D72M that simulates pushbuttons. Additionally, twelve TSI signals