HD404849 Datasheet, PDF (91/127 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404849 Series
Serial mode register B (SMRB: $028)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
—
— Undefined 0
—
—
W
W
Not used Not used SMRB1 SMRB0
SMRB1
0
1
Output level control in idle states
Low level
High level
SMRB0
0
1
Transmit clock division ratio
Prescaler output divided by 2
Prescaler output divided by 4
Figure 71 Serial Mode Register B (SMRB)
Serial Data Register (SRL: $006, SRU: $007): The serial data register configuration is shown in figures
72 and 73. This register has the following functions.
• 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 74.
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 72 Serial Data Register (SRL)
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