User`s guide

B: BSC 2780/3780 Control Procedures
DC 900-1340I 225
data source. Under external clocking, BSC receives its transmit clocks from the remote
computer. Under internal clocking, the transmit clock is internally generated and also
output to the remote computer. For internal clocking on the Freeway 2000/4000, the
hardware clock jumper for each link must be set as described in the Freeway
ICP6000R/ICP6000X Hardware Description manual. If you need to set internal clocking,
call the Protogate customer support number given in the Preface. For the Freeway 1000,
refer to the ICP2424 Hardware Description and Theory of Operation.
Ta ble B –2 defines the EIA-232 clock signals used by the BSC software.
B.6 Idle Line Condition
When no data is being transmitted on a full-duplex circuit, the transmit line is held in
a marking condition (all one-bits are transmitted).
Table B– 1: EIA-232 Modem Control Lines
Signal Pin Direction Description
RTS 4 Output For half-duplex, RTS is turned on just before
transmission is started and turned off when trans-
mission is complete.
CTS 5 Input CTS is checked after RTS is turned on but prior to
transmit. If CTS is on at this point, transmit is
started and further changes in the CTS pin are
ignored until the next block is ready to be trans-
mitted. If CTS is off at this point, transmission is
delayed until the CTS pin is turned on.
DSR 6 Input DSR is monitored by the BSC software and its sta-
tus is reported in the link status report.
DCD 8 Input DCD is monitored by the BSC software, and its sta-
tus is reported in the link status report.
DTR 20 Output DTR is turned on when the link is started and
turned off when the link is stopped.