NEC PD78F9488 User Manual
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CHAPTER 12 SERIAL INTERFACE 1A0
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User’s Manual U15331EJ4V1UD
(1) Serial I/O shift register 1A0 (SIO1A0)
This is an 8-bit register used to carry out parallel/serial conversion and to carry out serial
transmission/reception (shift operation) in synchronization with the serial clock.
SIO1A0 is set with an 8-bit memory manipulation instruction.
When the value in bit 7 (CSIE10) of serial operation mode register 1A0 (CSIM1A0) is 1, writing data to
SIO1A0 starts a serial operation.
During transmission, data written to SIO1A0 is output to the serial output (SO10). During reception, data is
read from the serial input (SI10) to SIO1A0.
RESET input sets SIO1A0 to 00H.
Caution Do not write data to SIO1A0 while the automatic transmit/receive function is activated.
(2) Automatic data transmit/receive address pointer 0 (ADTP0)
This register stores value of (transmit data byte
− 1) while the automatic transmit/receive function is activated.
As data is transferred/received, it is automatically decremented.
ADTP0 is set via an 8-bit memory manipulation instruction. The higher 4 bits must be set to 0.
RESET input makes ADTP0 undefined.
Caution Do not write data to ADTP0 while the automatic transmit/receive function is activated.
(3) Serial clock counter
This counter counts the serial clocks to be output and input during transmission/reception to check whether
8-bit data has been transmitted/received.