CHAPTER 14 SERIAL INTERFACE CHANNEL 1
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User’s Manual U11302EJ4V0UM
(3) Communication operation
(a) Basic transmission/reception mode
This transmission/reception mode is the same as the 3-wire serial I/O mode in which the specified
number of data are transmitted/received in 8-bit units.
Serial transfer is started when any data is written to serial I/O shift register 1 (SIO1) while bit 7
(CSIE1) of serial operating mode register 1 (CSIM1) is set to 1.
Upon completion of transmission of the last byte, the interrupt request flag (CSIIF1) is set. However,
the termination of automatic transmission/reception should be judged by bit 3 (TRF) of the automatic
data transmit/receive control register (ADTC), not CSIIF1.
If busy control and strobe control are not executed, the P23/STB and P24/BUSY pins can be used
as normal I/O ports.
Figure 14-8 shows the basic transmission/reception mode operation timing, and Figure 14-9 shows
the operation flowchart. The operation of the buffer RAM to transmit/receive 6-byte data is shown
in Figure 14-10.
Figure 14-8. Basic Transmission/Reception Mode Operation Timing
SCK1
SO1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF
SI1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Interval
Cautions 1. Because, in the basic transmission/reception mode, the automatic transmit/
receive function writes/reads data to/from the buffer RAM after 1-byte transmission/
reception, an interval is inserted until the next transmission/reception.
As the buffer RAM write/read is performed at the same time as CPU processing,
the maximum interval is dependent upon CPU processing and the value of the
automatic data transmit/receive interval specification register (ADTI) (see (5)
Automatic transmit/receive interval).
2. When TRF is cleared, the SO1 pin becomes low level.
Remark
CSIIF1: Interrupt request flag
TRF:
Bit 3 of the automatic data transmit/receive control register (ADTC)
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