UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 111

• Manufacturer Part Number: UPD75238GJ
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC [NEC]

PD75238
(b) Shift register 1 (SIO1)
SIO1 is an 8-bit register which performs parallel-serial conversion and serial transfer (shift)
operation in phase with the serial clock.
Serial transfer is started by writing data to SIO1.
In send operation, data written to SIO1 is output on the serial output (SO1). In receive operation,
data is read from the serial input (SI1) into SIO1.
Data can be read from or written to SIO1 using an 8-bit manipulation instruction.
When the RESET signal is entered during operation, the value of SIO1 is undefined. When the RESET
signal is entered in the standby mode, the value of SIO1 is preserved.
Shift operation is stopped after 8-bit send or receive operation is completed.
The timing for reading SIO1 and start of serial transfer (writing to SIO1) is as follows:
• When the serial interface operation enable/disable bit (CSIE1) is set to 1. However, the case where
CSIE1 is set to 1 after data is written to the shift register is excluded.
• When the serial clock is masked after 8-bit serial transfer
• When SCK1 is high
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