Thermo Scientific ThermoFlex Manual De Instrucciones página 181

Appendix C
All commands must be entered in the exact format shown in the tables on the following pages. The tables show
all commands available, their format and responses. Controller responses are either the requested data or an error
message. The controller response must be received before the host sends the next command.
The host sends a command embedded in a single communications packet, then waits for the controller's response.
If the command is not understood or the checksums do not agree, the controller responds with an error
command. Otherwise, the controller responds with the requested data. If the controller fails to respond within 1
second, the host should resend the command.
Note All byte values are shown in hex, hex represents the binary values that must be sent to the chiller. Do not
use ASCII.

The framing of the communications packet in both directions is:
Lead char Addr-MSB Addr-LSB Command n d-bytes
OxCA/OxCC
Lead char
Addr-msb
Addr-lsb
Command
n d-bytes
d-byte 1
...
d-byte n
Checksum
When a command has no value associated with it, (e.g., REQ ACK), "n d-bytes" will be set to 0. Values such
as temperature and flow are sent as either 2 or 4 byte signed integers, depending on how they are stored in the
controller RAM.
When the controller sends a value, a qualifier byte is sent first, followed by a 2 or 4 byte integer (the least
significant byte is sent last). The qualifier indicates the precision and units of the value. The host does not send
the qualifier byte; it must send the value using the correct precision, units and number of bytes. The host first
inquires about a value it wants to change, then uses the number of data bytes and the qualifier byte it receives to
generate the proper integer to send.
C-2 ThermoFlex
Checksum region
0xCA (RS-232) 0xCC (RS-485)
Device address is 1 (RS-232)
Most significant byte of slave address (RS-232: 0)
Least significant byte of slave address (RS-232: 1)
Command byte (see Table of Commands)
Number of data bytes to follow
1 data byte (the qualifier byte is considered a data byte)
st
...
n data byte.
th
Bitwise inversion of the 1 byte sum of bytes beginning with the
most significant address byte and ending with the byte preceding
the checksum. (To perform a bitwise inversion, "exclusive OR"
the one byte sum with FF hex.)
d-byte 1 ... d-byte n Checksum
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