HD404849 Datasheet, PDF (88/125 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404849 Series
Serial mode register A (SMRA: $005)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
0
0
0
0
W
W
W
W
SMRA3 SMRA2 SMRA1 SMRA0
SMRA3
0
1
R2₁/SCK
mode selection
R2₁
SCK
Prescaler
SMRA2 SMRA1 SMRA0 SCK Clock source division ratio
0
0
0
Output Prescaler
Refer to
table 29
1
1
0
1
1
0
0
1
1
0
Output System clock —
1
Input External clock —
Figure 70 Serial Mode Register A (SMRA)
Serial Mode Register B (SMRB: $028): This register has the following functions (figure 71).
• Prescaler division ratio selection
• Output level control in idle states
Serial mode register B (SMRB: $028) is a 2-bit write-only register. It cannot be written during data
transfer.
By setting bit 0 (SMRB0) of this register, the prescaler division ratio is selected. Only bit 0 (SMRB0) can
be reset to 0 by MCU reset. Bit 1 (SMRB1) is used to control the output level of the SO pin in idle states.
The output level changes at the same time that SMRB1 is written to.
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