Marquee 8521 Ultra Green (HUD) User's Manual
B-6
Marquee Projectors RS-232 Control
B.6.3 Optional
Checksum
It is no longer necessary to calculate and include an eight-bit additive sum as the next-to-last byte in
every data transmission. Note that you must still include the checksum
field
in each message
stream, but if the value assigned is “$00” the checksum will be ignored. If you still wish to use an
accurate checksum for maximum message security, calculate the checksum value as follows:
1. Take the message before the transport layer bytes have been added.
2. Add the bytes together.
3.
Divide the sum by 256 and take the remainder. The remainder value is the
checksum.
The receiving projector software collects all of the message bytes as defined in the first byte of the
message, then creates its own checksum value for comparison with the received checksum. If the
values match, the message is considered to have been correctly received—otherwise the message
is discarded.
Note:
NOTE: Transport layer bytes including ESC (and the resultant top bit set) are NOT
included in the checksum. See Transport Layer.
B.6.4 Command
Codes
Table B-3 4 lists all 1-byte hex command codes now available on the Marquee. The first column
identifies each projector control, with the applicable set/request/reply command codes listed in the
next two columns — one of these codes appears as the first byte after the header in any message.
The fourth column lists any parameters that may apply to the function at hand, with P1 representing
the first parameter of the data sent (such as switcher number), P2 representing the second
parameter of the data sent (such as slot number) and P3 representing the third parameter (such as
vertical frequency). These bytes follow the command code byte. The last column briefly describes
what each “set” command does.
Note:
Each parameter allows a limited range of values — these values are shown in Table B-3 in
decimal format
.
Note:
The projector will convert any out-of-range value to the nearest maximum value allowed.
For example, “set color to 100” will set the color to its maximum value of 63.
Note:
Values are treated as unsigned. So -1 in a byte is treated as 255.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
