HD404639R Datasheet, PDF (97/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

Serial mode register 2A (SM2A: $01B)
Bit
Initial value
Read/Write
Bit name
3
0
W
SM2A3
2
0
W
SM2A2
1
0
W
SM2A1
0
0
W
SM2A0
HD404639R Series
SM2A3
0
1
R5₁/SCK₂
mode selection
R5₁
SCK₂
SM2A2
0
1
SM2A1 SM2A0
0
0
1
1
0
1
0
0
1
1
0
1
SCK₂
Output
Output
Input
Clock source
Prescaler
Prescaler
division ratio
Refer to
table 27
System clock —
External clock —
Figure 77 Serial Mode Register 2A (SM2A)
Serial Mode Register 2B (SM2B: $01C): This register has the following functions (figure 78).
• Serial interface 2 prescaler division ratio selection
• Serial interface 2 output level control in idle states
• R5₃/SO₂ pin PMOS control
Serial mode register 2B is a 3-bit write-only register. It cannot be written during serial interface 2 data
transfer. Bit 0 (SM2B0) and bit 2 (SM2B2) are reset to $0 by MCU reset.
By setting bit 0 (SM2B0) of this register, the serial interface 2 prescaler division ratio of serial interface 2 is
selected. By resetting bit 1 (SM2B1), the output level of the SO₂ pin is controlled in idle states of serial
interface 2. The output level changes at the same time that SM2B1 is written to.
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