APPENDIX D: COMMUNICATION CODES
UNIFLOW
®
4 PULSED HEAT CONTROL
990-908 D-3
When you issue a command to the Control, you need to wait about 250 ms. before you issue the next
command. The answer timeout is set to about 250 ms. in case the Control doesn’t respond to a
command.
Error checking at the unit is as follows:
1. If the Control decodes an RS-485 address that does not match the unit’s address, the
command is ignored.
2. The Control will ignore an external command that does not end with an <eot> or one that
does not have the correct number of data bytes specified in the message.
3. If the Control reflows during reception or transmission of a command there is a
possibility that bytes may be missed or the message truncated.
4. Unsupported commands will return a Nak #3.
5. Incorrect checksums will return a Nak #2.
6. If the Control is dropping incoming characters, the Control may return either a Nak #1, #2
or #4 depending on which character was dropped.
7. When the temperature data in the DS command is set to ‘0’, or any of the data is out of
range, the Control will return a Nak #6.
Suggested error checking procedure on the external host side of the interface:
1. For a host “read” command, e.g. read profile data, the host must timeout if the unit does
not send a complete response within a reasonable amount of time. Host can also check
the number of bytes received against the expected number for that message, range check
the received data, or do whatever else is thought necessary to have confidence in the
received data.
2. Following a host “set” command, the host must subsequently read the data just “set” and
make sure the data “set” matches data “read.” For example, if a “set profile 1” command
is sent, the unit must then do a “read profile 1” and compare the set data against the read
data.
Significance of the Unit’s COMMUNICATIONS ROLE Parameter on the
Communications Screen:
1. This parameter must be set to
MASTER under normal running conditions to turn on the “Read
Report” command which sends the results of the latest reflow to the host automatically.
2. When the parameter is set to
SLAVE, this reporting will be turned off and the unit will accept
both “Read” and “Set” from the host.
3. When MASTER, the unit will not accept any commands from the host. This avoids potential
collisions between these commands and the automatic reporting of reflow results.
4.
MASTER or SLAVE must be set at the Control panel by pressing the SETUP key and selecting
option 2:
COMMUNICATIONS.
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