ICS ELECTRONICS 4809A, Instruction Manual

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3-3
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appropriate register enable bits are set true, then the 4899A will generate a
Service Request by asserting the SRQ line. The SRQ line stays asserted until
the 4899A is serial polled or until the bits that caused the SRQ are reset.
3.2.2 4809A Differences
The 4809A is a 4.5 by 5.5 inch board that mounts inside a chassis or tem-
perature chamber. It is functionally identical to the 4899A and has both
RS-232 and RS-422/RS-485 serial interfaces. The 4809A's baud rate is
limited to 38,400 baud.
3.2.3 4819A Differences
The 4819A mounts on the rear panel and has both a GPIB and an external
serial connector which extends the Modbus serial path to the rear panel
of the host chassis. The user can control an RS-232 Modbus device from
the serial connector or from the 4819A’s GPIB interface. However, both
interfaces cannot be used at the same time. Once the GPIB interface is
activated, the serial interface cannot be used to control the Modbus device
until the 4819A has been powered off and back on.
3.2.4 4829A Differences
Like the 4819A, the 4829A mounts on the rear panel of the host chassis and
has both a GPIB and an external RS-232 serial connector which extends
the Modbus serial path to the rear panel of the host chassis. The user can
control one to several RS-485 Modbus device(s) from the serial connec-
tor or from the 4829A’s GPIB interface. However, both interfaces cannot
be used at the same time. Once the GPIB interface is activated, the serial
interface cannot be used to control the Modbus device until the GPIB con-
nection is removed.
3.3 ADDRESSING THE UNITS