AM79C202 Legerity, AM79C202 Datasheet - Page 9

• Manufacturer Part Number: AM79C202
• Description: (AM79C202 / AM79212) PCM CODEC
• Manufacturer: Legerity

Pin Names
IRTA, IRTB
S0, S1, S2
VLBIAS
VCCA
VCCD
VOUT
VREF
ISUM
VINM
IREF
RST
VIN
VM
O1
Output
Output
Output
Output
Output
Output
Type
Power
Power
Inputs
Input
Input
Input
Input
Input
Current Reference. An external resistor (RREF) connected between this pin and analog
ground generates an accurate on-chip reference current. This current is used by the
ASLAC device in its DC Feed and loop-supervision circuits.
Ring-Trip Sense. These pins are current summing nodes referenced to VREF. They pro-
vide terminations for external resistors RSR1 and RSR2 that sense the voltages on both
sides of the ringing-feed resistor connected to the ring bus. To determine the ringing cur-
rent in the loop, the ASLAC device finds the difference between the currents in these pins.
Metallic Sense. ISUM is a current input pin and is fed by the ISUM pin of the ASLIC device.
The current in this pin is used by the ASLAC device for supervisory and diagnostic func-
tions.
Control Port. This output port is TTL compatible and is controlled by the O1 bit (bit 2) in
the downstream C/I channel. It can control an external logic device or it can be connected
to pin C3, C4, or C5 of the ASLIC device to control relays.
Reset. A logic 1 on this pin resets the ASLAC device to initial default conditions. A signal
less than 100 ns in duration should not cause a reset. To ensure proper reset, the mini-
mum length of a reset pulse is 50 µs.
GCI Channel Identification Straps. When the input pins are individually strapped to VCC
or DGND, the ASLAC device can be coded to communicate with one of the eight GCI
channels within a frame.
Analog Power Supply. VCCA is internally connected to substrate near the analog I/O
section.
Digital Power Supply. VCCD is internally connected to substrate near the digital section.
Analog Input. The analog output (VTX) from the ASLIC device is applied to the ASLAC
device transmit path input, VIN. The signal is sampled, processed, encoded, and placed
on the upstream GCI port.
Inversion of Analog Input. An inverted version of the analog input voltage on VIN appears
on this pin.
Longitudinal Reference. VLBIAS is programmed by VOFF and supplies the longitudinal
reference voltage for the longitudinal control loop to the ASLIC device.
12 kHz or 16 kHz Metering Signal. For 12 kHz or 16 kHz teletax, an internally generated
and shaped 12 kHz or 16 kHz sine wave metering pulse is output from this pin.
Analog Output. The voice data from the downstream GCI port, B1 channel, is digitally
processed and converted to an analog signal that is sent out of the VOUT pin to the
ASLIC device.
Analog Reference. This pin provides a voltage reference to be used as the analog zero-
level reference on the ASLIC device.
ASLIC/ASLAC Products
Description
9