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CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
μ
PD78018F SUBSERIES)
(9) Transfer start
Serial transfer is started by setting the transfer data to the serial I/O shift register 0 (SIO0) when the following
two conditions are satisfied:
Operation control bit of serial interface channel 0 (CSIE0) = 1
Internal serial clock is stopped or SCK0 is high after 8-bit serial transfer
Cautions 1. Transfer is not started even when CSIE0 is set to “1” after data has been written to SIO0.
2. Because the N-ch open-drain output must be made high-impedance state during data
reception, write FFH to SIO0 in advance.
However, when the wake-up function specification bit (WUP) = 1, the N-ch open-drain
output is always at high-impedance state, and FFH needs not to be written to SIO0 before
reception.
3. If data is written to SIO0 when the slave is busy, that data is not lost.
When SB0 (or SB1) input goes high (ready) after the busy status has been released,
transfer is started.
When 8-bit transfer has been completed, serial transfer is automatically stopped, and an interrupt request flag
(CSIIF0) is set.
Be sure to perform the following setting to the pin that is used to input/output data (SB0 or SB1) before serial
transfer of 1 byte after the RESET signal has been input:
<1> Set 1 to the output latches of P25 and P26.
<2> Set bit 0 (RELT) of the serial bus interface control register (SBIC) to 1.
<3> Set 0 to the output latches of P25 and P26 to which 1 has been set before.
(10) Method to judge busy state of a slave
Check whether a slave is in the busy status from the device in the master mode, in the following procedure:
<1> Detect generation of the acknowledge signal (ACK) or interrupt request signal.
<2> Set the port mode register PM25 (or PM26) of the SB0/P25 (or SB1/P26) pin in the input mode.
<3> Read the status of the pin (if the pin is high, it is in the ready status).
After detecting the ready status, set 0 to the port mode register, to restore the output mode.