Intelix
DIGI-HD-8X8
Installation Manual
16 www.intelix.com
difference between the value and the ESCAPE byte. Example; If value =>
ESCAPE, then value = (value - ESCAPE). These two bytes are transmitted
instead of the single, large-value byte. The receiving device converts the two
bytes back into the original single byte value through simple addition.
These
operations do not affect the values of the length or checksum fields. i.e., The
Escape byte algorithm is applied to the message string last on transmission and
first upon receipt (skipping the start byte).
In the following example, the data field of a message is (02h, 03h, 03h, 06h,
FFh). The byte FFh must be “escaped” into the ESCAPE byte (F0h) followed by
the difference between FFh and ESCAPE (FFh – F0h = 0Fh). The bytes actually
transmitted are: (02h, 03h, 03h, 06h, F0h, 0Fh). Since the second byte of an
escape sequence must fall within the range 00h through 0Fh inclusive, any
second byte outside of that range indicates that a transmission error has
occurred, and the Ack byte will not be sent.
Non-escaped example:
Serial_Start Length
Class
Message
ID Input
Output
Target Value
F1h 05h 02 03h 03h 02h F6h
Escaped example:
Serial_Start Length
Class
Message
ID Input
Output
Target Value
F1h 05h 02 03h 03h 02h F0h
06h
Reserved Bytes
The following table lists the bytes which have special meaning in all Intelix
Serial Message protocols:
FF Reserved
FE Error
FD
ACK (Version 4 sequence bit 1)
FC
Version 3 ACK (Version 4 sequence bit 0)
FB
Start byte (Version 2 protocol)
FA
Start byte (Version 3 protocol)
F9
Start byte (Version 3 escaped protocol)
F8
Start byte (Version 4 protocol)
F7 Reserved
F6 Reserved
F5 Reserved
F4 Reserved
F3 Reserved
F2 Reserved
F1
Start bytes (simple escaped protocol)
F0 Escape
byte
Simple Escaped RS232 Com Port Communication Details
115200 baud
8 data bits
1 stop bit
No parity
DCE unit (straight through serial cable)
