2.4.2 Read Text Packets (continued)
9. If the client receives a Success Command (
A0
) text packet, the client returns an acknowledgment (
ACK
/
0x06
)
to indicate that it is ready to receive data. If the client receives a Failure Command (
A2
) text packet, the client
must restart the communication process by sending an Enquiry (
ENQ
/
0x05
) to the dispenser.
10. When the acknowledgment (
ACK
/
0x06
) from the client is received, the dispenser sends a text packet that
contains the data requested by the client.
EXAMPLE:
(STX) + 05 + D0 + 001 + 96 + (ETX)
The above text packet in hexadecimal format is shown below:
STX
0
5
D
0
0
0
1
9
6
ETX
0x02
0x30
0x35
0x44
0x30
0x30
0x30
0x31
0x39
0x36
0x03
11. When the client receives the text packet, the client can either transmit another text packet or the client can
transmit End of Text (
EOT
/
0x04
) to end the sequence.
Diagram of Read Text Packet Communication between the Client and Dispenser
Communication Flow
Client
(PC / PLC)
Ultimus V
dispenser
ENQ (0x05)
ACK (0x06)
EOT (0x04)
STX
(0x02)
0
2
A
0
2
D
ETX
(0x03)
STX
(0x02)
0
4
U
A
space
(0x20)
space
(0x20)
C
6
ETX
(0x03)
ACK (0x06)
STX
(0x02)
0
5
D
0
0
0
1
9
6
ETX
(0x03)
NOTES:
• The
STX
(
0x02
) and
ETX
(
0x03
) control characters are
not
added when sending
ENQ
(
0x05
),
ACK
(
0x06
),
NAK
(
0x15
), or
EOT
(
0x04
). These are stand-alone / single-byte control characters.
•
Communication Timeout:
The client sends an Enquiry (
ENQ
/
0x05
) to the dispenser and receives an
acknowledgment (
ACK
/
0x06
) in response. The next text packet (such as the
UA--
text packet shown
previously) must be sent by the client within 2 seconds, otherwise the dispenser enters a Communication Timeout
state and responds with an Failure Command (
A2
) text packet.
Appendix B — RS‑232 Protocol (continued)
Ultimus V High Precision Fluid Dispenser
49
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