sp301ct Exar Corporation, sp301ct Datasheet - Page 13

• Manufacturer Part Number: sp301ct
• Description: Rs-232/rs-422 Line Drivers/receivers
• Manufacturer: Exar Corporation

LOOPBACK
Both the SP301 and SP302 have a function called
loopback, which is essentially a chip self-test. How-
ever, by connecting system test loops with the inputs
and outputs of the SP301/302, a system-level diag-
nostic can be run on power-up or on command. The
SIGNAL PROCESSING EXCELLENCE
Two -Channel Full Duplex RS-232
RS-232 LINE DRIVERS
RS-232 RECEIVERS
Corporation
ROA
ROB
TIA
TIB
SELECT A = 0
SELECT B = 0
LB = 1
SP301 CONFIGURATIONS IN LOOPBACK MODE
TOA
TOB
RIA
RIB
1
1
1
1
test loops can be enabled and disabled allowing both
system test and operation with the same components.
A maximum data rate for loopback of 3kbps is
recommended. Loopback is a pin-programmable func-
tion, activated by a logic low on the LB pin (19). As
One-Channel Full Duplex RS-232 &
One-Channel Full Duplex RS-422
RS-422 LINE DRIVER
RS-422 RECEIVER
RS-232 LINE DRIVER
RS-232 RECEIVER
TIB
ROB
TIA
ROA
V
EE
10k
10k
SELECT A = 0
SELECT B = 1
LB = 0
(ACTIVE)
TOA
TOB
TOB
RIA
RIB
RIB
1
1
2
1
2
1
10k
10k
10k
10k
V
V
EE
EE
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