M38203M4 Datasheet, PDF (234/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.6 Serial I/O2
2.6.2 Pins
The serial I/O2 uses 4 pins, namely, pins for data transmit, data receive, shift clock transmit/receive, and
receive enable signal output. All these pins are also used as port P5 and switched their functions by the
serial I/O2 port selection bit (bit 3), SRDY2 output enable bit (bit 4) and synchronization clock selection bit
(bit 6) of the serial I/O2 control register (address 001D16).
The function of each pin is described below.
(1) Data transmit pin [SOUT2]
This pin outputs each bit of transmit data and is used as port P51. When the serial I/O2 port selection
bit (bit 3) of the serial I/O2 control register is set to “1,” this pin functions as a serial I/O2 data output
pin.
(2) Data receive pin [SIN2]
This pin inputs each bit of receive data and is used as port P50. There is no register for selecting
between port function and data input pin function. Clear bit 5 of the port P5 direction register to “0”
(input mode).
(3) Shift clock transmit/receive pin [SCLK2]
This pin inputs (receives from the outside) or outputs (supplies to the outside) a shift clock used for
transmission and reception.
When the synchronization clock selection bit (bit 6) of the serial I/O2 control register is set to “0” (use
of external clock), a shift clock is input from the outside. When this bit is set to “1” (use of internal
clock), a shift clock is output to the outside.
(4) Receive enable signal output pin [SRDY2]
This pin notifies the outside of the receive enable state in the clock synchronous mode.
This pin functions as the receive enable signal output pin by setting the SRDY2 output enable bit (bit
4) of the serial I/O2 control register to “1.”
The pin level changes from “H” to “L” at the timing which data is written into the serial I/O2 register,
notifying the outside of the receive enable state.
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3820 GROUP USER’S MANUAL