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Intermec EasyCoder 501 – Service Manual Ed. 7
Chapter 21 RS-422/485 Interface Board
+ RS422 IN
- RS422 IN
+ RS422 OUT
- RS422 OUT
+ RS485 OUT
- RS485 OUT
21.1 Description, cont.
Communication Port "uart2:"
This port can be used for either RS-422 or RS-485 interface:
RS-422 is a point-to-point serial interface, which can connect one
printer to a host computer at a distance of up to 1,200 metres
(4,000 ft.) using a four-wire screened cable. The transmission is
full duplex, that is, simultaneous transmission and reception.
Simplifi ed example of an RS-422 connection.
RS-485 is a serial interface that allows up to 32 units to be con-
nected in a multi-drop loop consisting of a two-wire screened cable
with a max. length of 1,200 metres (4,000 ft.) and branching con-
nections of max. 2 metres (6.5 ft.). The transmission is half duplex,
that is, transmission and reception cannot take place simultane-
ously.
Simplifi ed example of an RS-485 connection.
A transmission of data can be addressed to a certain unit in an
RS-485 multi-drop loop, provided the “Prot. addr” setup option is
enabled. Each printer must be given an address by means of straps
on the interface board. See Intermec Fingerprint v6.13, Program-
mer’s Guide.
In an RS-485 loop, one of the units must be appointed “master”
unit. Usually, the host computer is the master. If not (check the
manual for the host), one printer can be appointed master by fi tting
two straps on the interface pcb.
The fi rst and last unit must be fi tted with one termination strap.
Communication Port "uart3:"
This port always contains an RS-232 serial interface. Ex5V
(max 200 mA) can be connected using a strap.
Note:
The RS-422/485 communication
port is in most cases referred to
as "uart2:", except in connec-
tion with the OPEN statement,
when it must be referred to as
"rs485:".