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Table 2-9
R6684-17 Pin Descriptions (MDP) (continued)
Pin Name
Pin Type
-RLYB
OD
(-TALK)
Speaker Interface
SPKR
O(DF)
(MSPKR)
Diagnostic Signals
EYEXY
OA
-EYECLK
OA
EYESYNC
OA
Pin No.
28
Relay B (Voice) Control. The MDP -RLYB output is
connected to the Voice relay (DPDT). In voice mode, the
modem asserts the this output to switch the handset from the
telephone line to a current source to power the handset so it
can be used as a microphone and speaker interface to the
modem.
The -RLYB output can directly drive a +5V reed relay coil with
a minimum resistance of 360Ω and having a must-operate
voltage of no greater than 4.0 Vdc. A damp diode, such as a
1N4148, should be installed across the relay coil. An external
transistor, such as an MPSA20, can be used to drive heavier
loads (e.g., electro-mechanical relays).
29
Modem Speaker Analog Output. The SPKR output reflects
the received analog input signal. The SPKR is controlled by
the ATMn command. The SPKR output can drive an
impedance as low as 300Ω. In a typical application, the
SPKR output is an input to an external LM386 audio power
amplifier.
48
Serial Eye Pattern W/Y Output. EYEXY is a serial output
containing two 15 bit diagnostic words (EYEX and EYEY) for
display on the oscilloscope X axis (EYEX) and Y axis (EYEY).
47
Serial Eye Pattern Clock. -EYECLK is a 288 kHz output
clock for use by the serial-to-parallel converters.
46
Serial Eye Pattern Strobe. EYESYNC is a strobe for loading
the D/A converters.
Descriptions
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