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Apalis Carrier Board Design Guide
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Figure 48: IrDA Reference Schematic
2.15.3 Unused UART Signal Termination
Unused UART interface signals can be left unconnected. For debugging purpose, it is
recommended to have at least the UART1_RXD and UART1_TXD signals available.
2.16 SPI
The serial peripheral interface (SPI) bus is a synchronous, full duplex interface. The Apalis module
form factor features two independent SPI interfaces. Each of these interfaces has one chip select
signal as compatible standard. Some modules may feature an additional chip select signal or
additional SPI interfaces as secondary function of other pins.
The clock polarity and phase of the SPI bus is not standardized. Some peripherals latch the data at
the positive edge of the clock while others latch it at the negative edge. The SPI modes describe
these different behaviors. Make sure that the relevant Apalis module and the peripheral devices
are set to the same SPI mode.
SPI Mode
Clock
Polarity
Clock
Phase
Description
0
0
0
Clock has positive polarity and the data is latched at the positive edge of SCK
1
0
1
Clock has positive polarity and the data is latched at the negative edge of SCK
2
1
0
Clock has negative polarity and the data is latched at the positive edge of SCK
4
1
1
Clock has negative polarity and the data is latched at the negative edge of SCK
Table 27: SPI Modes
MM70-314-310B1
UART1_RXD
118
Apalis - UART
10 of 25
UART1_TXD
112
UART1_CTS
116
UART1_RTS
114
UART1_DCD
124
UART1_DSR
120
UART1_DTR
110
UART1_RI
122
UART2_RXD
132
UART2_TXD
126
UART2_CTS
130
UART2_RTS
128
UART3_RXD
136
UART3_TXD
134
UART4_RXD
140
UART4_TXD
138
X1J
22R
R10
22R
R11
TFDU4101
LED_A
1
LED_K
2
TXD
3
RXD
4
SD
5
VCC
6
NC
7
GND
8
X30
22R
R66
0R
R67
4.7uF
10V
+ C62
100nF
16V
C57
GND
R69
100K
GND
UART4_IRDA_SD
R68
4.7R
IrDA Transceiver
3.3V_SW
3.3V_SW
UART4_IRDA_LED
UART4_IRDA_VCC
UART4_RXD
UART4_TXD