NEC uPD78P078 User Manual
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CHAPTER 19 SERIAL INTERFACE CHANNEL 1
Figure 19-7. Circuit of Switching in Transfer Bit Order
Start bit switching is realized by switching the bit order write to SIO1. The SIO1 shift order remains
unchanged. Thus, MSB-first and LSB-first must be switched before writing data to the shift register.
(4) Transfer start
Serial transfer is started by setting transfer data to the serial I/O shift register 1 (SIO1) when the following
two conditions are satisfied.
•
Serial interface channel 1 operation control bit (CSIE1) = 1
•
Internal serial clock is stopped or SCK1 is a high level after 8-bit serial transfer.
Caution If CSIE1 is set to “1” after data write to SIO1, transfer does not start.
Upon termination of 8-bit transfer, serial transfer automatically stops and the interrupt request flag (CSIIF1)
is set.
7
6
Internal Bus
1
0
LSB-first
MSB-first
Read/Write Gate
SI1
Shift Register 1 (SIO1)
Read/Write Gate
SO1
SCK1
D
Q
SO1 Latch