272
Sine waves are output from a high-precision resistor-ladder-type D/A converter. Each cycle is
divided into 32 segments to give a stable waveform with low distortion.
•
Composite or single waveform output
Register settings can select combined row-and-column-group output, or independent row-
group or column-group output.
11.1.2
Block Diagram
Figure 11.2 shows a block diagram of the DTMF generator.
DTLR
Clock
counter
400 kHz
(1.2 MHz to 10 MHz, selectable
in 400-kHz steps)
D/A sine-wave
counter
Modified
programmable
divider
DTCR
Feedback
Column section
Feedback
TONED
VT
ref
f
OSC
Internal data bus
Row section
DTLR:
DTCR:
DTMF load register
DTMF control register
D/A sine-wave
counter
Modified
programmable
divider
Legend:
Figure 11.2 DTMF Generator Block Diagram