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S1C63558 TECHNICAL MANUAL EPSON 117
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Telephone Function)
The row group and column group dividers can be operated individually. The software can select one of
them to output a single tone signal as well as a dual tone signal output. Use the SINR (FF16H•D1) and
SINC (FF16H•D0) registers for this control.
Table 4.14.4.3 Tone output selection
SINR
0
0
1
1
Control register
SINC
0
1
0
1
Tone output
DC level: 1/2 (V
DD
–V
SS
)
COL frequency
ROW frequency
Dual tone output
At initial reset, dual tone output is set.
The divided frequencies are converted into a tone signal through the sine-wave ROM and the D/A
converter, then the tone signal is output from the TONE terminal.
The items to set before outputting a tone signal may be summarized as follows:
1. Setting tone mode ... It is not necessary if the mode has not be changed after an initial reset.
2. Selecting a tone output method (single tone/dual tone) ... SINR and SINC are used.
3. Turning the OSC3 oscillation circuit ON (OSCC = "1") ... Note
Note: The OSC3 oscillation needs at least 5 msec until it is stabilized after the OSC3 oscillation circuit is
turned ON. Therefore, dialing operations must be started after taking an interval of at least 5 msec
from activation of the OSC3 oscillation circuit. Since the oscillation stabilization time varies de-
pending on the external oscillator's characteristic and operating conditions, allow ample margin for
the interval.
Further the OSC3 oscillation circuit increases current consumption, so it should be turned OFF
when the DTMF generator is not used or the CPU does not need high-speed processing.
The following explains how to output the tone signal and the circuit operation.
First, write "1" to the HSON register (FF18H•D3) so the dialer is in off-hook status. As a result, the DP
terminal goes High (V
DD) level.
Next, write the ROW/COL data of the pushbutton to be transmitted to the TCD3–TCD0 register (FF17H).
Table 4.14.4.4 shows the relationship of write data and tone frequencies.
Table 4.14.4.4 Tone frequency selection
D3
0
0
0
0
0
0
0
0
D2
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
TCD code
Tone frequency
(ROW1, COL4)
(ROW1, COL1)
(ROW1, COL2)
(ROW1, COL3)
(ROW2, COL1)
(ROW2, COL2)
(ROW2, COL3)
(ROW3, COL1)
Key
symbol
"A"
"1"
"2"
"3"
"4"
"5"
"6"
"7"
D3
1
1
1
1
1
1
1
1
D2
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
TCD code
Tone frequency
(ROW3, COL2)
(ROW3, COL3)
(ROW4, COL2)
(ROW4, COL3)
(ROW4, COL1)
(ROW2, COL4)
(ROW4, COL4)
(ROW3, COL4)
Key
symbol
"8"
"9"
"0"
"#"
"*"
"B"
"D"
"C"
Writing data to this register triggers the start of the tone output. When single tone output is selected,
either the ROW frequency or COL frequency corresponding to the written data is output as a tone signal.
When dual tone output is selected, the specified ROW and COL frequencies are output after they are
composed.
Figure 4.14.4.2 shows a timing chart for tone output.