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MSM66573 Family User's Manual
Chapter 12 Serial Port Functions
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SIO3 register (SIO3R)
The SIO3 register (SIO3R) is an 8-bit shift register that performs the shift operations during
transmission and reception.
Writing 8-bit data to SIO3R starts transmission and reception of SIO3.
SIO3R can be read from and written to by the program. Read the received data before
transmission and reception of the next data begins.
When reset (
RES signal input, execution of a BRK instruction, overflow of the watchdog
timer, opcode trap), the value of SIO3R is undefined.
[Note]
In the slave mode, write to SIO3R while the SIOCK3 pin is at a High level.
If new data is written to SIO3R during transmission and reception, the data currently being
transmit and receive will be destroyed.
Because writing to SIO3R triggers transmission and reception, write dummy data if only
reception is to be performed.
12.7.3 Example of SIO3-related Register Settings
Transmit-receive settings
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Port 10 mode register (P10IO)
If the master mode is to be used, set bit 0 (P10IO0) to "1" to configure that port as an output.
If the slave mode is to be used, reset bit 0 (P10IO0) to "0" to configure that port as an input.
Reset bit 1 (P10IO1) to "0" to configure that port as an input. Set bit 2 (P10IO2) to "1" to
configure that port as an output.
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Port 10 secondary function control register (P10SF)
If the master mode is to be used, set bit 0 (P10SF0) to "1" to configure that port as a
secondary function output. If the slave mode is to be used, specify with bit 0 (P10SF0)
whether that port is to be pulled-up. Specify with bit 1 (P10SF1) whether the SIOI3 pin is
to be pulled-up. Set bit 2 (P10SF2) to "1" to configure that port as a secondary function
output.
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SIO3 control register (SIO3CON)
Specify the SIO3 shift clock with bits 0 and 1 (SFT3CK0, SFT3CK1). Select master mode
or slave mode with bit 2 (SFT3SLV).
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SIO3 register (SIO3R)
In the case of transmission, write the data to be transmit. For reception, write dummy data.
Transmission and reception will begin after data is written to SIO3R.