HD404459 Datasheet, PDF (93/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

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
HD404459 Series
SMRB1
0
1
Output level control in idle states
Low level
High level
SMRB0
0
1
Serial clock division ratio
Prescaler output divided by 2
Prescaler output divided by 4
Figure 72 Serial Mode Register B (SMRB)
Serial Data Register (SRL: $006, SRU: $007): This register has the following functions (figures 73 and
74).
• 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 (figure 75); data is input, LSB first, through the SI pin at the rising edge of the transmit
clock.
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 73 Serial Data Register Lower Digit (SRL)
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