AM79231 Datasheet, PDF (19/28 Pages) List of Unclassifed Manufacturers – Intelligent Subscriber Line Interface Circuit (ISLIC)

Operating Modes
The Am79231 receives multiplexed control data on the P1, P2 and P3 pins. The LD pin then controls
the loading of P1, P2, and P3 values into the proper bits in the Am79231 control register. When the
LD pin is less than 0.3 V below VREF ( < (VREF – 0.3 V) ), P1–P3 must contain data for relay control
bits RD1, RD2 and RD3. These are latched into the first three bits in the Am79231 control register.
When the LD pin is more than 0.3 V above VREF (> (VREF + 0.3 V) ), P1–P3 must contain ISLIC
control data C1, C2, and C3, which are latched into the last three bits of the Am79231 control register.
Connecting the LD pin to VREF locks the contents of the Am79231 control register.
The operating mode of the Am79231 is determined by the C1, C2, and C3 bits in the control register
of the Am79231. Table 1 defines the Am79231 operating modes set by these signals.
Under normal operating conditions, the ISLIC device does not have active relays. The Am79231 to
ISLAC device interface is designed to allow continuous real-time control of the relay drivers to avoid
incorrect data loads to the relay bit latches of the Am79231 devices.
To perform external ringing, the ISLAC device from the Intelligent Access voice family is set to external
ringing mode (RMODE = 1), enables the ring relay, and puts the Am79231 in the Standby mode.
Table 1. Operating Modes
C3 C2 C1 Operating Mode
0 0 0 _Standby¹
0 0 1 _{Tip Open}¹
0 1 0 On-Hook Transmis-
sion, Fixed Longitudi-
nal Voltage
0 1 1 Disconnect
1 0 0 RSVD
1 0 1 Active High Battery
1 1 0 Active Low Battery
1 1 1 RSVD
Battery Voltage
Selection
High Battery
(BATH) and BGND
High Battery
(BATH) and BGND
High Battery
(BATH) and BGND
Operating Mode
(High ohmic feed): Loop supervision
active, A and B amplifiers shut down
Tip Open: AD at High-Impedance,
Channel A power amplifier shut down
Fixed longitudinal voltage of –30 V
Connection to
RMGPi & RMGLi
Resistors
Open
Open
Low Battery
selection at VBL
AD and BD at High-Impedance,
Channel A and B power amplifiers
shut down
High Battery
(BATH) and BGND
Low Battery
(BATL) and BGND
Active feed, normal or reverse
polarity
A and B Amplifier
Output
Note:
1. In these modes, the ring lead (B-lead) output has a –50 V internal clamp to battery ground (BGND).
Am79231 Data Sheet
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