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Safety Ground
6-6 Reference.
Supported
Modems
The electrical safety or
earth
ground, and the signal ground . are wholly
separate. The signal ground is carried in a dedicated conductor for each
port. The electrical ground is common for
all
ports and is wired from pin
1 at each port to pin 1 in the RS-232-C panel 62-pin connector. This pin
is
then connected to the cable metallic shield, which, in turn, is connected to
the computer chassis ground.
As explained in Chapter 1, the MUX complies with RS-232-C and CCITT
V.24 standards for communications. Table 6-2 classifies the supported
modem lines. Both RS-232-C and CCITT V.24 identify a circuit irrespec-
tive of point of view. The mnemonics used in this manual are identified
as
seen from the computer end of the circuit.
Each of the six channels of the multiplexer controls and monitors seven
modem control lines. Various designations for the two data lines, the sig-
nal ground, and these control lines are correlated in Table 6-1. Table 6-3
lists the pin assignments for the RS-232-C cable ports on the junction
panel. All six ports are wired the same way, internal traces route the sig-
nal to the proper pins on the 62-pin conector at the top of the panel.
Table 6-2. Modem Unes Supported by the UP 27140A
RS·231-C
CCITT
Mnemonic
Description
I/O
V.l4
Code
BB
104
RD
Received Data
I
BA
103
SD
Send Data
0
CB
106
CS
Clear to Send
I
CF
109
RR
Received Line Signal Detector I
CC
107
DM
Data Set Ready (Data Mode)
I
CE
125
IC
Ring Indicator
I
CA
105
RS
Request to Send
0
CD
108.2
TR
(Data) Terminal Ready
0
CHICI
111/112
SR
Select Rate
AB
102
SG
Signal Ground
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