490
CHAPTER 20 SERIAL INTERFACE CHANNEL 2
(3) MSB/LSB switching as the start bit
The 3-wire serial I/O mode enables to select transfer to start from MSB or LSB.
Figure 20-13 shows the configuration of the transmit shift register (TXS/SIO2) and internal bus. As shown
in the figure, MSB/LSB can be read/written in reverse form.
MSB/LSB switching as the start bit can be specified with bit 2 (CSIM22) of the serial operating mode register
2 (CSIM2).
Figure 20-13. Circuit of Switching in Transfer Bit Order
Start bit switching is realized by switching the bit order for data write to SIO2. The SIO2 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 transmission shift register (TXS/SIO2) when the
following two conditions are satisfied.
• Serial interface channel 2 operation control bit (CSIE2) = 1
• Internal serial clock is stopped or SCK2 is a high level after 8-bit serial transfer.
Caution If CSIE2 is set to “1” after data write to TXS/SIO2, transfer does not start.
Upon termination of 8-bit transfer, serial transfer automatically stops and the interrupt request flag (SRIF)
is set.
7
6
Internal Bus
1
0
LSB-first
MSB-first
Read/Write Gate
SI2
Transmit Shift Register (TXS/SIO2)
Read/Write Gate
SO2
SCK2
D
Q
SO2 Latch
Summary of Contents for PD78076
Page 2: ...2 MEMO ...
Page 12: ...12 MEMO ...
Page 48: ...48 MEMO ...
Page 64: ...64 MEMO ...
Page 82: ...82 MEMO ...
Page 100: ...100 MEMO ...
Page 130: ...130 MEMO ...
Page 180: ...180 MEMO ...
Page 222: ...222 MEMO ...
Page 248: ...248 MEMO ...
Page 288: ...288 MEMO ...
Page 308: ...308 MEMO ...
Page 364: ...364 MEMO ...
Page 494: ...494 MEMO ...
Page 526: ...526 MEMO ...
Page 544: ...544 MEMO ...
Page 558: ...558 MEMO ...
Page 580: ...580 MEMO ...
Page 596: ...596 MEMO ...
Page 598: ...598 MEMO ...
Page 626: ...626 MEMO ...