TWR-K21D50M Freescale Semiconductor, TWR-K21D50M Datasheet - Page 10

• Manufacturer Part Number: TWR-K21D50M
• Description: Development Boards & Kits - ARM
• Manufacturer: Freescale Semiconductor

Specifications of TWR-K21D50M

• Rohs: yes
• Product: Development Boards
• Tool Is For Evaluation Of: MK21DN512VMC5
• Core: ARM Cortex M4
• Interface Type: USB
• Operating Supply Voltage: 1.8 V/3.3 V
• Description/function: TWR-K21D50M MCU module is designed to work either in stand-alone mode or as part of the Freescale Tower System
• For Use With: Freescale Tower Systems

6.3 Clocking
Kinetis K Series MCUs start up from an internal digitally controlled oscillator (DCO). Software can enable the main
external oscillator (EXTAL0/XTAL0) if desired. The external oscillator/resonator can range from 32.768 KHz up to 32
MHz. An 8-MHz crystal is the default external source for the MCG oscillator inputs (XTAL/EXTAL).
A 32.768-kHz crystal is connected to the RTC oscillator inputs by default.
By populating isolation resistors, other external clock sources for the K21DN512VMB5 include the CLKIN0 signal,
which can be provided through the TWR-ELEV module or pin 20 of TWRPI connector J3.
6.4 System Power
When installed into a Tower System, the TWR-K21D50M can be powered from either an on-board source or from
another source in the assembled Tower System.
In stand-alone operation, the main power source (5.0 V) for the TWR-K21D50M module is derived from either the
OSJTAG USB micro-B connector (J2) or the K21DN512VMB5 USB micro-AB connector (J19). Two low-dropout
regulators provide 3.3 V and 1.8 V supplies from the 5.0 V input voltage. Additionally, the 3.3 V regulator built into
the K21DN512VMB5 MCU can be selected to power the 3.3 V bus. All of the user-selectable options can be
configured using two headers, J11 and J17. Refer to sheet 5 of the TWR-K21D50M schematics for more details.
DryIce and RTC VBAT
The DryIce tamper detection module and the Real Time Clock (RTC) module on the K21DN512VMB5 have two modes
of operation: system power-up and system power-down. During system power-down, the tamper detection module
and the RTC are powered from the backup power supply (VBAT) and electrically isolated from the rest of the MCU.
The TWR-K21D50M provides a battery receptacle for a coin cell battery that can be used as the VBAT supply. This
receptacle can accept common 3-V lithium coin cell batteries that are 20 mm in diameter.
6.5 Debug Interface
There are two debug interface options provided: the on-board OSJTAG circuit and an external ARM JTAG connector.
The ARM-JTAG connector (J1) is a standard 2x10-pin connector that provides an external debugger cable access to
the JTAG interface of the K21DN512VMB5. Alternatively, the on-board OSJTAG debug interface can be used to access
the debug interface of the K21DN512VMB5.
6.6 OSJTAG
An on-board MC9S08JM60 based Open Source JTAG (OSJTAG) circuit provides a JTAG debug interface to the
K21DN512VMB5. A standard USB A male to micro-B male cable (provided) can be used for debugging via the USB
connector (J2). The OSJTAG interface also provides a USB to serial bridge. Drivers for the OSJTAG interface are
provided in the P&E Micro OSBDM/OSJTAG Tower Toolkit. These drivers and more utilities can be found online
.
at
http://www.pemicro.com/osbdm
TWR-K21D50M Tower Module User’s Manual
Page 10 of 16