HD404669 Datasheet, PDF (88/142 Pages) Hitachi Semiconductor – Low-Voltage AS Microcomputers with On-Chip DTMF Generation Circuit

HD404669 Series
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
SM1B1
0
1
Output level control in idle states
Low level
High level
SM1B0
0
1
Transmit clock division ratio
Prescaler output divided by 2
Prescaler output divided by 4
Figure 63 Serial Mode Register 1B (SM1B)
Serial Data Register 1 (SR1L: $006, SR1U: $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 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 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 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
SR1L3 SR1L2 SR1L1 SR1L0
Figure 64 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
SR1U3 SR1U2 SR1U1 SR1U0
Figure 65 Serial Data Register 1 (SR1U)
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