14-3
Seiko Epson Corporation
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
14.2.3.
Pin Functions in Master Mode and Slave Mode
The pin functions are changed according to the master or slave mode selection. The differences in pin
functions be- tween the modes are shown in Table 14.2.3.1.
Table 14.2.3.1 Pin Function Differences between Modes
Pin
Function in master mode
Function in slave mode
SDI
n
Always placed into input state.
SDO
n
Always placed into output state.
This pin is placed into output state while a low level
is applied to the #SPISS
n
pin or placed into Hi-Z
state while a high level is applied to the #SPISS
n
pin.
SPICLK
n
Outputs the SPI clock to external devices.
Output clock polarity and phase can be configured
if necessary.
Inputs an external SPI clock.
Clock polarity and phase can be designated accord-
ing to the input clock.
#SPISS
n
Not used.
This input function is not required to be assigned to
the port. To output the slave select signal in master
mode, use a general-purpose I/O port function.
Applying a low level to the #SPISS
n
pin enables
SPIA to transmit/receive data. While a high level is
applied to this pin, SPIA is not selected as a slave
device. Data input to the SDI
n
pin and the clock
input to the SPICLK
n
pin are ignored. When a high
level is applied, the transmit/receive bit count is
cleared to 0 and the already received bits are dis-
carded.
14.2.4.
Input Pin Pull-Up/Pull-Down Function
The SPIA input pins (SDI
n
in master mode or SDI
n
, SPICLK
n
, and #SPISS
n
pins in slave mode) have a
pull-up or pull-down function as shown in Table 14.2.4.1. This function is enabled by setting the
SPIA_
n
MOD.PUEN bit to 1.
Table 14.2.4.1 Pull-Up or Pull-Down of Input Pins
Pin
Master mode
Slave mode
SDI
n
Pull-up
Pull-up
SPICLK
n
–
SPIA_
n
MOD.CPOL bit = 1: Pull-up
SPIA_
n
MOD.CPOL bit = 0: Pull-down
#SPISS
n
–
Pull-up
Summary of Contents for S1C31D50
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