HD404654 Datasheet, PDF (77/111 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

Serial mode register 1B (SM1B: $028)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
—
— Undefined 0
—
—
W
W
Not used Not used SM1B1 SM1B0
HD404654 Series
SM1B1
0
1
Output level control in idle states
Low level
High level
SM1B0
0
1
Serial clock division ratio
Prescaler output divided by 2
Prescaler output divided by 4
Figure 57 Serial Mode Register 1B (SM1B)
Serial Data Register 1 (SR1L: $006, SR1U: $007): This register has the following functions (figures 58
and 59)
• Serial interface 1 transmission data write and shift
• Serial interface 1 receive data shift and read
Writing data in this register is output from the SO₁ pin, LSB first, synchronously with the falling edge of
the transmit clock; data is input, LSB first, through the SI₁ pin at the rising edge of the transmit clock.
Input/output timing is shown in figure 60.
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 1 (lower digit) (SR1L: $006)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
R/W
R/W
R/W
R/W
SR13 SR12 SR11 SR10
Figure 58 Serial Data Register 1 (SR1L)
Serial data register 1 (upper digit) (SR1U: $007)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
R/W
R/W
R/W
R/W
SR17 SR16 SR15 SR14
Figure 59 Serial Data Register 1 (SR1U)
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