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7.3. Computer interactive interfacing: main protocol
This section defines fully the serial communications protocol implemented in the Format
550 Controller used on Sanyo Gallenkamp chambers and rooms. This protocol allows
a master computer (System Master) to communicate with one or more Controllers on a
network.
Typical applications include:
where the chamber is required to operate interactively with the test proce-
dure being applied to the test load within the chamber
where a simple record of the conditions of the chamber is required di-
rectly into a logging system already being used.
The document describes in detail what a master computer should do to comply with the
protocol.
This makes no assumption about the functionality of the master software. A particular
Host Software package is available separately.
The protocol is defined in four layers:
Physical Layer defining electrical connections between controller & master
Frame Layer defining byte frame structure
Packet Layer defining information flow between controller & master
Information Layerdefining syntax of information passed
7.3.1 PHYSICAL LAYER DEFINITION
The medium used to connect Controllers) to master depends on:
the distance between master & Controller
the number of Controllers
Master to single Controller: Up to 50 feet RS232
Up to 1000 feet RS485
Master to several Controllers: RS485 bus.
The Chamber itself has a 25 pin RS232 port (connector 'D' type DTE) which is used
for communicating with the master. A RS232 to 485 adapter is used when a RS485
hook up is required. The adapter uses the RS232's RTS line to control the data direction
oftheRS485port.
7.3.2 COMMUNICATIONS FRAME DEFINITION
19,200 baud
1 start bit
8 data bits
0 parity bits
1 stop bit
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