User's Manual

C1 March 2010
M7
RS-485 receivers have built-in bias resistors, offering the network a true
“1/8 unit load”. In most allocations, these internal bias resistors are sufficient,
and an external bias resistor is not required.
Phoenix Contact/Tyco makes a convenient DB-9 to terminal-block connector,
part number 2761839.
4.6. RS422/EIA-422 Serial I/O Connector
RS-422 communications uses 4-wire differential signals. The RS422 9-pin
s
erial I/O connector is a female 9-p D-subminiature connector having the
following pins configuration.
Front-view of DB-9 connector on modem (female)
Pin # Name Dir Function Level / Specification
1
- Do not connect Do not connect this pin to anything.
2
B (
-
)
In B Inverting RS-485 data in line
3
Out -
out
Z Inverting data out pin
4
A (+)
in A Non-inverting RS-485 data in line
5
GND Ground Connect to earth ground.
6
- Do not connect Do not connect this pin to anything.
7
Out +
out
Y No-inverting data out
8
9
Vin
In/Out
DC Power
DC Power in or out if unit is powered using DC
in jack.
Configuring for RS-422
To configure the M7 modem for RS-422 operation, use the ATIO 4 command.
You must order the RS-422 option for this to work, and only M7 modems with
Revision E or higher hardware will work in RS-422 mode. The M7’s hardware
is identical to the RS-485 version, with the exception of two internal loop-back
resistors.
Raveon’s RS-422 I/O circuit uses 3.3V logic to drive the lines, and the RS422
pins are ESD protected to ±15kV and 7kV human body model
.
RS-422 installations typically have a termination resistor across the In and the
Out lines. A value of 150 ohms should work in most applications.
Bias and Termination Resistors
M7 RS-422 receivers have built-in bias resistors, offering the network a true
“1/8 unit load”. In most allocations, these internal bias resistors are sufficient,
and an external bias resistor is not required.
Serial out data comes out pins 3 and 7. Serial input data comes in via pins 4
and 8. Connect pin 5 to earth ground.