TWR-K40X256 Freescale Semiconductor, TWR-K40X256 Datasheet - Page 9

• Manufacturer Part Number: TWR-K40X256
• Description: TOWER SYSTEM BOARD K40X256
• Manufacturer: Freescale Semiconductor
• Series: Kinetisr
• Type: MCUr

Specifications of TWR-K40X256

• Contents: Board
• Processor To Be Evaluated: K40
• Data Bus Width: 32 bit
• Interface Type: USB, CAN, I2C, SPI, UART
• Dimensions: 3.5 in x 3.2 in
• Operating Supply Voltage: 1.71 V to 3.6 V
• Silicon Manufacturer: Freescale
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M4
• Silicon Core Number: MK
• Silicon Family Name: Kinetis - K40
• Kit Contents: Board Only
• Rohs Compliant: Yes
• For Use With/related Products: Freescale Tower System, K40X256
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 clocking circuitry on the TWR-K40X256 is shown on sheet 4 of the schematics and in Figure 6. An
8.0 MHz ceramic resonator with built-in load capacitors is the default external source for the MCG
oscillator inputs (XTAL/EXTAL_MAIN). A 32.768 KHz crystal is connected to the RTC oscillator inputs by
default. There are optional resistors (not populated by default) to allow for the MCG oscillator inputs
to be routed from any one of the 8.0 MHz resonator, the 32.678 KHz crystal, or the clock input pin
CLKIN0 from the Primary Connector (pin B24). Table 1 shows the resistor settings for each of the MCG
oscillator input options.
USB full-speed/low-speed OTG/Host/Device controller with device charge detect
SPI, I
SD Host Controller (SDHC)
GPIO with pin interrupt support, DMA request capability, digital glitch filtering
Capacitive touch sensing inputs (TSI)
LCD display driver supporting 3V and 5V glass, configurable frontplane and backplane pins, and
segment failure detection
Debug interfaces: JTAG, cJTAG, SWD
Trace: TPIO, FPB, DWT, ITM, ETM, ETB
2
C (w/ SMBUS support), UART (w/ ISO7816 and IrDA), CAN, I
2
TWR-K40X256 Tower Module User's Manual
8
C31
C37
X3
8.00MHZ
8MHz_XTL
8MHz_EXTL
CLKIN0
DNP
DNP
18PF
18PF
Figure 6. External clock source circuitry
R89
0
Y 3
32.768KHz
32KHz_XTL
32KHz_EXTL
8MHz_XTL_R
R85
1.0M
R94
1.0M
DNP
R93
R91
R95
R97
R87
R86
R83
R84
DNP
DNP
DNP
DNP
0
0
0
0
0
0
0
0
2
S
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XTAL32_RTC
EXTAL32_RTC
XTAL_MAIN
EXTAL_MAIN