參數(shù)資料
型號(hào)： AM79D2251JC
廠商： ADVANCED MICRO DEVICES INC
元件分類： 編解碼器
英文描述： Dual Intelligent Subscriber Line Audio-Processing Circuit (ISLAC)
中文描述： PCM CODEC, PQCC44
封裝： PLASTIC, LCC-44
文件頁數(shù)： 8/35頁
文件大小： 410K
代理商： AM79D2251JC
8
Am79D2251
CS/RST
Chip Select/Reset
I
For PCM backplane operation, a logic low on this pin for 15 or more DCLK cycles resets
the sequential logic in the ISLAC device into a known mode. A logic low placed on this pin
for less than 15 DCLK cycles is a chip select and enables serial data transmission into or
out of the DIO port. For GCI operation, a logic low on this pin
—
for 1 ms or longer
—
resets
the sequential logic into a known mode. See Table 2-4 in the Technical Reference for
details. 5 V tolerant.
Resistors that sense the high, low and positive battery voltages connect here. If only one
negative battery is used, connect both resistors at the supply. If the positive battery is not
used, leave the pin unconnected. These pins are current inputs whose voltage is held at
VREF.
For PCM backplane operation, TSCA is active low when PCM data is output on the DXA
pin. The outputs are open-drain and are normally inactive (high impedance). Pull-up loads
should be connected to VCCD. When GCI mode is selected, one of two GCI modes may
be selected by connecting TSCA/G to DGND or VCCD.
SHB, SLB,
SPB
Battery Sense
I
TSCA
/G,
Timeslot Control A/GCI
Mode, Time Slot
Control B
O
(PCM)
I
(GCI)
I
VSAB1
–
VSAB2
VCCA1
–
VCCA2
VCCD
Loop voltage sense
Connect to the VSAB pins of two ISLIC devices.
Power Supply
+3.3 VDC supplies to the analog sections in each of the two channels.
Power Supply
+3.3 VDC supply to all digital sections.
VREF
Analog Reference
O
This pin provides a 1.4 V, single-ended reference to the two ISLIC devices to which the
ISLAC device is connected.
High-level loop control voltages on these pins are used to control DC-feed, internal ringing,
metering and polarity reversal for each ISLIC device.
Analog transmit signals (VTX) from each ISLIC device connect to these pins. The ISLAC
device converts these signals to digital words and processes them. After processing, they
are multiplexed into serial time slots and sent out of the DXA/DU pin.
Normally connected to VCCA internally. They supply longitudinal reference voltages to the
ISLIC devices during certain test procedures. These outputs are connected internally to
VCCA during ISLIC Active, Standby, Ringing, and Disconnect modes. During test modes,
it can be connected to the receive D/A.
The IMT and ILG pins of two ISLIC devices connect to the VIMT1
–
VIMT4 and VILG1
–
VILG4
pins of the ISLAC chip. These pins are voltage inputs referenced to VREF. They
require external resistors connected between each pin and VREF to convert IMTn and
ILGn into voltages.
The ISLAC device extracts and processes voice data from time slots on DRA/DD serial
data port. After processing, the ISLAC device converts the voice data to analog signals
that are sent out of these pins to each respective ISLIC device.
External resistors connect here that sense an external voltage. In a linecard with external
ringing, they are used to sense the voltage at the line side of the ring-feed resistor. These
pins are current inputs whose voltage is held at VREF. An internal resistor converts currents
flowing in these pins into voltages to be sampled by the A/D.
An external resistor connects here that senses a common reference for external voltages
sensed by resistors connected to XSB1
–
XSB4. This pin is a current input whose voltage
is held at VREF. An internal resistor converts current flowing in this pin into a voltage to
be sampled by the A/D. This pin is intended for sensing external ringer supply voltages.
However, it can also be used to sense other test points when internal ringing is used.
VHL1
–
VHL2
VIN1
–
VIN2
High Level D/A
O
TX Analog
I
VLB1
–
VLB2
Longitudinal
Reference
O
VIMT1
–
VIMT2,
VILG1
–
VILG2
VOUT1
–
VOUT2
Sense
I
RX Analog
O
XSB1
–
XSB2
External Sense
I
XSC
Common External
Sense
I
Pin
Pin Name
I/O
Description
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