HD404669 Datasheet, PDF (94/142 Pages) Hitachi Semiconductor – Low-Voltage AS Microcomputers with On-Chip DTMF Generation Circuit

HD404669 Series
Tone Generator Control Register (TGC: $01A): The tone generator control register (TGC: $01A) is a 3-
bit write-only register that controls starting and stopping of DTMF signal generation as shown in figure 72.
TGC is initialized to 000- by an MCU reset or in stop mode, watch mode, or subactive mode. TONEC
output and TONER output are controlled individually by TGC3 and TGC2, and overall DTMF control is
performed by TGC1.
Tone generator control register (TGC: $01A)
Bit
Initial value
Read/Write
Bit name
3
0
W
TGC3
2
0
W
TGC2
1
0
0
—
W
—
TGC1 Not used
TGC3
0
1
TONEC output control (column)
No output
TONEC output (active)
TGC1
0
1
DTMF enable bit
DTMF disable
DTMF enable
TGC2
0
1
TONER output control (row)
No output
TONER output (active)
Figure 72 Tone Generator Control Register (TGC)
System Clock Select Registers 1 and 2 (SSR1: $029 and SSR2: $02A): The system clock select registers
1 and 2 (SSR1: $029 and SSR2: $02A) are 4-bit write-only registers. Applications must set these registers
to the values shown in figure 73 that correspond to the frequency of the oscillator circuit connected to the
OSC₁ and OSC₂ pins. If the oscillator frequency and the system clock select register settings differ from the
combination shown in figure 73, the DTMF output frequencies will not have the correct values as shown in
figure 71.
Except for the SSR13 bit, the system clock select registers 1 and 2 (SSR1: $029 and SSR2: $02A) are
initialized to $0 by an MCU reset or when the MCU switches to stop mode.
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