HD404459 Datasheet, PDF (92/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 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
R4₁/SCK
SMRA3 mode selection
0
R4₁
1
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 71 Serial Mode Register A (SMRA)
Serial Mode Register B (SMRB: $028): This register has the following functions (figure 72).
• 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. By setting bit 1 (SMRB1), the output level of the SO pin is controlled in idle
states of the serial interface. The output level changes at the same time that SMRB1 is written to.
90