MITSUBISHI MICROCOMPUTERS
M37274EFSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
Internal clock : The serial I/O counter is set to “7” during the write
External clock : The an external clock is selected as the clock source,
the interrupt request is set to “1” after the transfer clock has been
counted 8 counts. However, transfer operation does not stop, so the
clock should be controlled externally. Use the external clock of 500kHz
or less with a duty cycle of 50%.
cycle into the serial I/O register (address 021416), and the transfer
clock goes “H” forcibly. At each falling edge of the transfer clock after
the write cycle, serial data is output from the SOUT pin. Transfer di-
rection can be selected by bit 5 of the serial I/O mode register. At
each rising edge of the transfer clock, data is input from the SIN pin
and data in the serial I/O register is shifted 1 bit.
The serial I/O timing is shown in Figure 20. When using an external
clock for transfer, the external clock must be held at HIGH for initial-
izing the serial I/O counter. When switching between an internal clock
and an external clock, do not switch during transfer. Also, be sure to
initialize the serial I/O counter after switching.
After the transfer clock has counted 8 times, the serial I/O counter
becomes “0” and the transfer clock stops at HIGH. At this time the
interrupt request bit is set to “1.”
Notes 1: On programming, note that the serial I/O counter is set by
writing to the serial I/O register with the bit managing in-
structions, such as SEB and CLB.
2: When an external clock is used as the synchronous clock,
write transmit data to the serial I/O register when the trans-
fer clock input level is HIGH.
Synchronous clock
Transfer clock
Serial I/O register
write signal
(Note)
Serial I/O output
D
0
D
1
D
2
D
3
D
4
D
5
D
6
D7
SOUT
Serial I/O input
S
IN
Interrupt request bit is set to “1”
Note : When an internal clock is selected, the S OUT pin is at high-impedance after transfer is completed.
Fig. 20. Serial I/O Timing (for LSB first)
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RENESAS [ RENESAS TECHNOLOGY CORP ]
