MT3170B/71B, MT3270B/71B, MT3370B/71B
Serial Data (SD) Output
F
LOW
F
HIGH
DIGIT
b
3
b
2
b
1
b
0
When a valid DTMF signal burst is present, ESt or
DStD will go high. The application of four clock
pulses on the ACK pin will provide a 4-bit serial
binary code representing the decoded DTMF digit on
the SD pin output. The rising edge of the first pulse
applied on the ACK pin latches and shifts the least
significant bit of the decoded digit on the SD pin.
The next three pulses on ACK pin will shift the
remaining latched bits in a serial format (see Figure
5). If less than four pulses are applied to the ACK
pin, new data cannot be latched even though ESt/
DStD can be valid. Clock pulses should be applied
to clock out any remaining data bits to resume
normal operation. Any transitions in excess of four
pulses will be ignored until the next rising edge of the
ESt/DStD. ACK should idle at logic low. The 4-bit
binary representing all 16 standard DTMF digits are
shown in Table 1.
Powerdown Mode (MT317xB/337xB)
The MT317xB/337xB devices offer a powerdown
function to preserve power consumption when the
device is not in use. A logic high can be applied at
the PWDN pin to place the device in powerdown
mode. The ACK pin should be kept at logic low to
avoid undefined ESt/DStD and SD outputs (see
Table 2).
697
697
697
770
770
770
852
852
852
941
941
941
697
770
852
941
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
1633
1633
1633
1633
1
2
3
4
5
6
7
8
9
0
*
#
A
B
C
D
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0= LOGIC LOW, 1= LOGIC HIGH
Table 1. Serial Decode Bit Table
Note:
b0=LSB of decoded DTMF digit and shifted out first.
ACK (input)
low
low
high
high
+
PWDN (input)
low
high
+
low
high
ESt/DStD (output)
Refer to Fig. 4 for
timing waveforms
low
low
undefined
SD (output)
Refer to Fig. 4 for
timing waveforms
low
undefined
undefined
MT317xB/337xB
status
normal operation
powerdown mode
undefined
undefined
Table 2. Powerdown Mode
=enters powerdown mode on the rising edge.
Frequency 1 (Hz)
350
425
400
480
440
480
440
480
Frequency 2 (Hz)
440
---
---
620
---
620
480
620
On/Off
continuous
continuous
continuous
0.5s/0.5s
0.5s/0.5s
0.25s/0.25s
2.0s/4.0s
0.25s/0.25s
Description
North American Dial Tones
European Dial Tones
Far East Dial Tones
North American Line Busy
Japanese Line Busy
North American Reorder Tones
North American Audible Ringing
North American Reorder Tones
Table 3. Call Progress Tones
4-6
MITEL [ MITEL NETWORKS CORPORATION ]
