ViaSat 3862, Руководство по эксплуатации и обслуживанию, Страница: 119 / 173

Each message contains a 1- to 3-letter mnemonic which indicates the purpose of the message.
Most of the messages also require a 'W' (to write data) or an 'R' (to read data). Data may be read
at any time by the host, but the ACU must be in the REMOTE mode of operation before any
writes to the servo board are allowed. Writes to the ORI may be made at any time.
Following the 'W' or 'R' are various fields which are shown in the individual paragraphs. Write
commands require data fields, whose formats vary according to the message. One or more data
fields may be written, using commas as the field separator. Commas with no data fields preced-
ing them may be used to skip fields. For example, 'W,,0002' will store data in the third element
of whatever data set is being written without modifying the first two elements.
When optional multiple data fields are specified in the command, writing more than one data
field will result in data being written to the next logical element. For example, commands writ-
ing data to axis-dependent fields (POS, CMD, etc.) will write the optional data to the next se-
quential axis: @8MOD W3,1 will write a 3 to axis A and a 1 to axis B. Read commands may
optionally include a character indicating the number of data items to be read. However, the num-
ber of data items to be read plus the optional element pointer of the command must not exceed
the total number of elements in the set; for example, @8MOD B R3 is acceptable, since the ele-
ment pointer is set to axis B and 3 elements are requested (B, C, and D).
Responses from the ACU always begin with the '@' character, followed by the PWB ID indicat-
ing which board is responding (see the paragraph above). The next character will be an <ack> to
indicate a successful message transaction or an <nak> to indicate that there was a problem with
the host message. No other information is given with the <nak> to indicate the nature of the
problem.
For successful read transactions, the requested data fields follow the <ack> in a format dictated
by the message. Data fields are separated by commas, and the last field is always followed by a
final comma before the <cr><lf>.
NOTE
In general, all references to axis A apply to the Azimuth axis and
all references to axis B apply to the Elevation axis.
A.2 COMMUNICATION WITH A HOST COMPUTER
The host computer communications commands are listed in Table A.1.1. The number preceding
the command in the list corresponds with the paragraph number in which a description of the
command may be found.
In general, paragraphs A-2.1 through A-2.6 deal with commands for the ORI board exclusively.
Commands in paragraphs A-2.7 and A-2.8 may be sent to either the ORI or servo boards. Com-
mands in paragraphs A-2.9 through A-2.46 may be sent to only the servo board. The remainder
of the commands are specific to this application.
3862 Autotrack Controller
A-2 REMOTE INTERFACE COMMANDS
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