NEC PD78058FY(A) - Manual (Page 329)

329
CHAPTER 16 SERIAL INTERFACE CHANNEL 0 (
µ
PD78058F SUBSERIES)
(9) Transfer start
Serial transfer is started by setting transfer data to the serial I/O shift register 0 (SIO0) when the following two
conditions are satisfied.
• Serial interface channel 0 operation control bit (CSIE0) = 1
• Internal serial clock is stopped or SCK0 is at high level after 8-bit serial transfer.
Cautions 1. If CSIE0 is set to “1” after data write to SIO0, transfer does not start.
2. When receiving data, it is necessary to set the N-ch open drain output in the high
impedance state, so please write FFH in SIO0 in advance. However, in the case of the
wake up function instruction bit (WUP) = 1, the N-ch open drain output is always in the
high impedance state, so it is not necessary to write FFH in SIO0 before reception.
3. If data is written to SIO0 when the slave is busy, the data is not lost.
When the busy state is cleared and SB0 (or SB1) input is set to the high level (READY)
state, transfer starts.
Upon termination of 8-bit transfer, serial transfer automatically stops and the interrupt request flag (CSIIF0)
is set.
Furthermore, after inputting RESET in the pin used as the data input and output (SB0 or SB1), be sure to make
the following settings before serial transmission of the first byte of data.
<1> Set 1 to the P25 and P26 output latches.
<2> Set 1 to bit 0 (RELT) of the serial bus interface control register (SBIC).
<3> Set 0 to the P25 and P26 output latches to swhich 1 was set.