Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 38
With I3=2:
#1J+<CR> ........ ; Valid command not requiring data response
<ACK>....... ; Acknowledging character
UUU<CR> .......... ; Invalid command
<BELL> ............. ; PMAC reports error
P1..3<CR> ...... ; Valid command requiring data response
25<CR>50<CR>75<CR><ACK>
; PMAC responds with requested data
With I3=3:
#1J+<CR> ........ ; Valid command not requiring data response
<ACK> ............... ; Acknowledging character
UUU<CR> .......... ; Invalid command
<BELL> ............. ; PMAC reports error
P1..3<CR> ...... ; Valid command requiring data response
<LF>25<CR><LF>50<CR><LF>75<CR><ACK>
.......................... ; PMAC responds with requested data
I4 Communications Integrity Mode
Range: 0 to 3
Units: None
Default: 1
This parameter permits Turbo PMAC to compute checksums of the communications bytes (characters)
sent either way between the host and Turbo PMAC, and also controls how Turbo PMAC reacts to serial
character errors (parity and framing), if found. Parity checking is only available on Turbo PMAC boards;
it is enabled only if jumper E49 is OFF.
The possible settings of I4 are:
Setting
Meaning
0
Checksum disabled, serial errors reported immediately
1
Checksum enabled, serial errors reported immediately
2
Checksum disabled, serial errors reported at end of line
3
Checksum enabled, serial errors reported at end of line
Communications Checksum: With I4=1 or 3, Turbo PMAC computes the checksum for
communications in either direction and sends the checksum to the host. It is up to the host to do the
comparison between PMAC's checksum and the checksum it computed itself. Turbo PMAC does not do
this comparison. The host should never send a checksum byte to Turbo PMAC.
Host-to-Turbo-PMAC Checksum: Turbo PMAC will compute the checksum of a communications line
sent from the host to Turbo PMAC. The checksum does not include any control characters sent (not even
the final Carriage-Return). The checksum is sent to the host immediately following the acknowledging
handshake character (<LF> or <ACK>), if any. Note that this acknowledging and handshake comes after
any data response to the command (and its checksum!). If Turbo PMAC detects an error in the line
through its normal syntax checking, it will respond with the <BELL> character, but will not follow this
with a checksum byte.
Note:
The on-line command <CTRL-N> can be used to verify the checksum of a
command line before the <CR> has been sent. The use of <CTRL-N> does not
affect how I4 causes Turbo PMAC to report a checksum after the <CR> has been
sent.