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3874 Group User's Manual
APPLICATION
2.5 Serial I/O
2.5.3 Clock synchronous serial I/O of serial I/O1
In the clock synchronous serial I/O mode, 8 shift clocks generated by the clock control circuit are used as
a synchronous clock for transfer. Synchronizing with these synchronous clocks, the transmit operation on
the transmitter and the receive operation on the receiver are simultaneously executed.
(1)
Clock synchronous serial I/O of serial I/O1 setting method
s Setting method at transmit
Figures 2.5.8 and 2.5.9 show the clock synchronous serial I/O of serial I/O1 setting method (at
transmit).
Fig. 2.5.8 Clock synchronous serial I/O of serial I/O1 setting method (at transmit) (1)
Process 1: Disable serial I/O transmit/receive interrupt.
Process 2: When BRG output/4 is selected as synchronous clock, set value to baud
rate generator.
b7
b0
Interrupt control register 2
(ICON2: address 3F16)
Key input, serial I/O1 transmit, and serial I/O1 receive interrupts disabled
(Interrupt of each vector disabled)
Process 3: Set serial I/O1 control register
b7
b0
1
Serial I/O1 control register
(SIO1CON: address 1A16)
BRG count source selected (set in internal clock selected)
0: f(XIN)
1: f(XIN)/4
Serial I/O1 synchronous clock selected
0: BRG output/4
1: External clock input
SRDY1 output enable selected
0: P47 pin operates as normal I/O pin
1: P47 pin operates as SRDY1 output pin
Transmit interrupt source selected
0: When transmit buffer has emptied
1: When transmit shift operation is completed
Transmit enabled (Note 1)
Receive enable selected
0: Receive disabled (at half-duplex communication)
1: Receive enabled (at full-duplex communication)
Clock synchronous serial I/O
Serial I/O1 enabled
(P44–P47 pins operate as serial I/O pins.)
(1) Disable interrupt of each vector
Note 1: When an external clock input is selected as the synchronous
clock, set “1” to the transmit enable bit while the synchronous clock is “H” state.
11
Baud rate generator
(BRG: address 1C16)
Set baud rate value
0
b7
b0
0
Interrupt source discrimination control register 1
(ICOND1: address 3916)
Serial I/O1 receive interrupt disabled
Serial I/O1 transmit interrupt disabled
(2) Disable interrupt of each interrupt factor
0