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APPENDIX
3874 Group User’s Manual
3.3 Notes on use
(3)
In automatic transfer serial I/O mode
s Set of automatic transfer interval
q When the SBUSY3 output is used, and the SBUSY3 output and the SSTB3 output function as signal for
each transfer data set by the SBUSY3 outputSSTB3 output function selection bit: the transfer interval
is necessary before the first data is transmitted/received, and after the last data is transmitted/
received. Accordingly, regardless of the contents of the SBUSY3 outputSSTB3 output function selection
bit, this transfer interval becomes 2 cycles longer than the value set for each 1-byte data.
q When using the SSTB3 output, regardless of the contents of the SBUSY3 outputSSTB3 output function
selection bit, this transfer interval becomes 2 cycles longer than the value set by the automatic
transfer interval set bit of the serial I/O3 control register 3 for each 1-byte data.
q When using the combined output of SBUSY3 and SSTB3 as the signal for each transfer data set, the
transfer interval after completion of transmission/reception of the last data becomes 2 cycles
longer than the value set by the automatic transfer interval set bit.
q Set the transfer interval of each 1-byte data transmission to 5 or more cycles of the internal
clock
φ after the rising edge of the last bit of a 1-byte data.
q When selecting an external clock, the automatic transfer interval cannot be set.
s Set of serial I/O3 transfer counter
q Write the value decremented by 1 from the number of transfer data bytes to the serial I/O3
transfer counter.
q When selecting an external clock, write a value to the serial I/O3 register/transfer counter, wait
for 5 or more cycles of internal clock
φ before inputting the transfer clock to the SCLK3 pin.
s Serial I/O initialization bit
A serial I/O3 interrupt request occurs when “0” is written to the serial I/O initialization bit during
an operation. Disable the interrupt enable bit as necessary by program.
(4)
Arbitrary bit serial I/O mode
s Set of serial I/O3 transfer counter
q Write the value decremented by 1 from the number of transfer data bytes to the serial I/O3
transfer counter.
q When selecting an external clock, write a value to the serial I/O3 register/transfer counter, wait
for 5 or more cycles of internal clock
φ before inputting the transfer clock to the SCLK3 pin.
s Set of automatic transfer interval
q When selecting an external clock, the automatic interval cannot be set.
q When using the SBUSY3 output, the transfer interval is necessary before the first data is transmitted/
received, and after the last data is transmitted/received. When using the SSTB3 output, this
transfer interval becomes 2 cycles longer than the value set for each 8-bit data. In addition,
when using the combined output of SBUSY3 and SSTB3, the transfer interval after completion of
transmission/reception of the last data becomes 2 cycles longer than the set value.
s Receive data
If the last data does not fill 8 bits, the receive data stored in the serial I/O3 automatic transfer RAM
becomes the closest MSB odd bit when the transfer direction select bit is set to LSB first, or the
closest LSB odd bit when the transfer direction select bit is set to MSB first.