SN75ALS085 Datasheet, PDF (2/17 Pages) Texas Instruments – LAN ACCESS UNIT INTERFACE DUAL DRIVER/RECEIVER

SN75ALS085
LAN ACCESS UNIT INTERFACE DUAL DRIVER/RECEIVER
SLLS054B – APRIL 1989 – REVISED MAY 1995
description (continued)
The purpose of the loop functions is to provide a means by which system data path verification can be done
to isolate faulty interfaces and assist in network diagnosis. The LOOP pins are TTL compatible and must be
held high for normal operation. When LOOP1 is taken low, the output of driver 1 (TXO1) immediately goes into
the idle state. Also, the input to receiver 1 is ignored and a path from TXI1 to RXO1 is established. When LOOP1
is taken back high, driver 1 and receiver 1 revert back to their normal operation. When LOOP2 is taken low, a
similar data path is established between TXI1 and RXO2. TXEN1 must be high for the loop functions to operate
and TXEN1 can be used to gate the loop function if desired. During loop operation, the respective receiver
enable output (RXEN) will reflect the status of TXEN1.
Function Tables
RECEIVER – LOOP = H
RXI
VID = 1315 mV to –175 mV,
tw < 25 ns
VID = –275 mV to –1315 mV, tw > 50 ns
VID = 318 mV to 1315 mV,
tw < 142 ns
VID = 318 mV to 1315 mV,
tw > 187 ns
H = high level, L = low level, X = don’t care
PREVIOUS RXEN
L
X
H
X
OUTPUTS
RXEN
RXO
L
H
H
L
H
H
L
H
DRIVER – LOOP = H
TXI
TXEN
PREVIOUS TXO
L
L
Idle
H
L
Idle
↓
H
Idle
L
H
Active
H < 260 µs
H
Active
H > 8 µs
H
Active
L
L > 8 µs
Active
H < 260 ns
L > 8 µs
Active
H < 260 ns
L < 260 ns
Active
H > 8 µs
L < 260 ns
Active
L
L < 260 ns
Active
H = VI ≥ VT max, L = VI ≤ VT min
OUTPUT TXO
Idle
Idle
L
L
H
Idle
Idle
Idle
H
Idle
L
2
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