Comtech EF Data HPCST-5000 - Manual (Page 153)

High-Power TWTA Satellite Terminals Programming Guide for Redundant Controller
Rev. 1 A–5
A.2.1.6 Check Byte
Select the calculation that matches the mode set with the Header Byte. The check byte
calculation choices are:
1. Calculation for Non-printable mode — The checksum is the “exclusive or”
(XOR) of all the message bytes including the header and ending bytes. Selecting
this option may result in the check byte not being a printable ASCII character.
2. Calculation for Printable mode — The check byte is calculated as follows:
a. Sum all of the message bytes.
b. Multiply the number of message bytes by 32. The message bytes include the
header byte, the ending byte, and all of the other bytes in between.
c. Subtract 2.b. from 2.a.
d. Take the modules of C (base 95) and add 32. This will always result in a
printable ASCII character in the range between 32 and 126.
A.2.1.7 Parity
COM1 (of both the controller and the TWTAs) is set for 8 bits, one stop bit, no parity.
COM2 can be customized to meet user requirements. All characters received by the
controller on COM2 are checked for even, odd, or no parity as defined by the user. The
default setting for COM2 is 8 bits, one stop bit, no parity. When active, a parity error in
any character will cause the command to be ignored.