HD404639R Datasheet, PDF (103/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

HD404639R Series
System Clock Select Registers 1 and 2 (SSR1: $029, SSR2: $02A): Four-bit write-only registers.
These registers must be set to the value specified in figures 85 and 86 depending on the frequency of the
oscillator connected to the OSC₁ and OSC₂ pins. Note that if the combination of the oscillation frequency
and the values in these registers is different from that specified in figures 85 and 86, the DTMF output
frequencies will differ from the correct frequencies as listed in table 28.
System clock select register 1 (SSR1: $029)
Bit
Initial value
Read/Write
Bit name
3
0
W
SSR13
2
0
W
SSR12
1
0
W
SSR11
0
0
W
SSR10
SSR13 32-kHz oscillation stop
0 Oscillation operates in stop mode
1 Oscillation stops in stop mode
32-kHz oscillation division
SSR12 ratio selection
0 f _SUB = f _X /8
1 f _SUB = f _X /4
System clock
SSR23 SSR22 SSR11 SSR10 selection
0
0
0
0 400 kHz
1 800 kHz
1
0 2 MHz
1 4 MHz
1 Don’t care Don’t care 3.58 MHz
1
0
1
1 8 MHz
1 Don’t care Don’t care 7.16 MHz
Figure 85 System Clock Select Register 1(SSR1)
101