CANOGA PERKINS 2240 Fiber Optic Modem User Manual
Page 45
Chapter 4 Data Interfaces
RS-449/422 Model 422
45
The SD, RD, ST, RT and TT pins carry the primary data and clock signals (conforming to the RS-
449 and RS-422 standards). In addition, an extra clock signal input (conforming to RS-422) is
provided to make the 2240/-422 combination more "DTE-like" in tail circuit applications at the
clock source end. The remainder of the pins are either ground references or control signals.
Send Data (SD) and Receive Data (RD) are the data input and output signals for the modem,
respectively.
Send Timing (ST) is the modem’s transmit clock reference output that is used for the internal and
slave clock modes. Receive Timing (RT) is the clock signal for the receive data unless the 2240’s
Table 4-3. RS-449 Pinouts
Pin
Number
A/B
RS-449 PIN
Name
(abbrev)
(full name)
Direction
1
SHLD
shield
-
4/22
SD
send data
to modem
5/23
ST
send timing
from modem
6/24
RD
receive data
from modem
7/25
RS
request to send
to modem
8/26
RT
receive timing
from modem
9/27
CS
clear to send
from modem
10
LL
local loopback
to modem
11/29
DM
data mode
from modem
12/30
TR
terminal ready
to modem
13/31
RR
receiver ready
from modem
14
RL
remote loopback
to modem
15
IC
incoming call
from modem
17/35
TT
terminal timing
to modem
18
TM
test mode
from modem
19
SG
signal ground
-
20
RC
receive common
- (tied to SG)
33
SQ
signal quality
from modem
34
NS
new signal
to modem
37
SC
send common
to modem
2/36*
N/A
extra clock for
receive data
to modem
* The extra clock is an enhancement added to -422 interfaces. Any -
422 interface card outfitted with this capability can be identified via
the lack of the W16/W15 BAL_CTRL jumper. The W16/W15 jumper
was never described in the manual, so do not try to find a reference
to it in the manual.