HD404669 Datasheet, PDF (87/142 Pages) Hitachi Semiconductor – Low-Voltage AS Microcomputers with On-Chip DTMF Generation Circuit

HD404669 Series
Serial mode register 1A (SM1A: $005)
Bit
Initial value
Read/Write
Bit name
3
0
W
SM1A3
2
0
W
SM1A2
1
0
W
SM1A1
0
0
W
SM1A0
SM1A3
0
1
R4₁/SCK₁
mode selection
R4₁
SCK₁
SM1A2 SM1A1 SM1A0
0
0
0
1
1
0
1
1
0
0
1
1
0
1
SCK₁
Output
Output
Input
Prescaler
Clock source division ratio
Prescaler
Refer to
table 20
System clock —
External clock —
Figure 62 Serial Mode Register 1A (SM1A)
Serial Mode Register 1B (SM1B: $028): This register has the following functions (figure 63).
• Serial clock division ratio selection
• High/low level control in idle states
Serial mode register 1B (SM1B: $028) is a 2-bit write-only register. It cannot be written during data
transfer.
Setting bit 0 (SM1B0) of the serial mode register 1B (SM1B: $028) selects the divisor applied to the
prescaler output used for the transfer clock. Only bit 0 (SM1B0) is cleared to 0 by an MCU reset or when
the MCU switches to stop mode.
Bit 1 (SM1B1) of the serial mode register (SM1B: $028) controls the high/low state of the SO₁ pin during
idle. The SO₁ pin changes state as soon as the high/low control bit is written. The value of this bit is
undefined after a reset or when the MCU enters stop mode.
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