3.1 No Response from the Dispenser (continued)
6. Check that you are using the correct command format, as explained under “2.6.2 Write Commands” on
page 51 and “2.6.3 Read Commands” on page 63.
7. Check that you are sending the Enquiry (
ENQ
/
0x05
) control character from the client to the dispenser as a
single-byte text packet (hexadecimal
0x05
), not as separate “E,” “N,” and “Q” characters.
NOTE:
This also applies to the
ACK
(
0x06
),
NAK
(
0x21
),
EOT
(
0x04
) control characters. Control characters
do not need
STX
(
0x02
) or
ETX
(
0x03
) added to them.
3.2 Dispenser Returns a Failure Command (A2)
1. Check that the length of the data and the checksum calculation is correct in the sent text packet. If the
checksum is incorrectly calculated, the dispenser discards the text packet and returns a Failure Command (
A2
)
response.
2. If the client sends an Enquiry (
ENQ
/
0x05
) text packet, the dispenser responds with an Acknowledgment
(
ACK
/
0x06
) text packet. However, if the client does not transmit the next text packet within 2 seconds, the
dispenser enters a Communication Timeout and responds with a Failure Command (
A2
).
To recover the communication, ensure that the length of the data and checksum calculation are correct, then
restart the communication by sending the Enquiry (
ENQ
/
0x05
) control character to the dispenser and following
the correct write / read communication sequence as explained under “2.4.1 Write Text Packets” on page 46
and “2.4.2 Read Text Packets” on page 48.
Appendix B — RS‑232 Protocol (continued)
Troubleshooting Remote Communication (continued)
Ultimus V High Precision Fluid Dispenser
76
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