HD404459 Datasheet, PDF (55/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 Series
Pins R4₁–R4₃ are multiplexed with peripheral pins SCK, SI, and SO, respectively. The peripheral function
modes of these pins are selected by bit 3 (SMRA3) of serial mode register A (SMRA: $005), and bits 0 and
1 (PMRA0, PMRA1) port mode register A (PMRA: $004) (figures 36 and 37).
Port mode register A (PMRA: $004)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
—
—
0
0
—
—
W
W
Not used Not used PMRA1 PMRA0
PMRA0
0
1
R4₃/SO mode selection
R4₃
SO
PMRA1
0
1
R4₂/SI mode selection
R4₂
SI
Figure 36 Port Mode Register A (PMRA)
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 port
1
SCK
SMRA2
0
SMRA1 SMRA0 SCK
0
0 Output
Clock source
Prescaler
Prescaler
division
ratio
÷2048
1 Output Prescaler
÷512
1
0 Output Prescaler
÷128
1 Output Prescaler
÷32
1
0
0 Output Prescaler
÷8
1 Output Prescaler
÷2
1
0 Output System clock —
1 Input External clock —
Figure 37 Serial Mode Register A (SMRA)
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