HD404369 Datasheet, PDF (84/117 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404369 Series
Serial Data Register (SRL: $006, SRU: $007): This register has the following functions (figures 64 and
65).
• Transmission data write and shift
• Receive data shift and read
Writing data in this register is output from the SO pin, LSB first, synchronously with the falling edge of the
transmit clock; data is input, LSB first, through the SI pin at the rising edge of the transmit clock.
Input/output timing is shown in figure 66.
Data cannot be read or written during serial data transfer. If a read/write occurs during transfer, the
accuracy of the resultant data cannot be guaranteed.
Serial data register (lower digit) (SRL: $006)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
R/W
R/W
R/W
R/W
SR3
SR2
SR1
SR0
Figure 64 Serial Data Register (SRL)
Serial data register (upper digit) (SRU: $007)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
R/W
R/W
R/W
R/W
SR7
SR6
SR5
SR4
Figure 65 Serial Data Register (SRU)
Transmit clock
Serial output
data
1
2
3
4
5
6
7
8
LSB
MSB
Serial input data
latch timing
Figure 66 Serial Interface Output Timing
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