Grass Valley Performer SD - Manual (Page 150)

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Section 3 — Operation & Service
Performer ASCII Protocol
Performer ASCII allows control of the Performer from a host
terminal or computer using standard ASCII characters. Multiple
Performers, each assigned a unique address, may be controlled
over a common RS422 bus. All characters are 7-bit ASCII (the
eighth data bit out of the Performer port is ignored). A ninth data
bit may be used for parity if desired.
Command Line
A command line consists of series of bytes in the following format:
<CR> <Adr Hi> <Adr Lo> <Len Hi> <Len Lo> <Data>
All bytes are hex ASCII (characters 0-9 [30H-39H] and A-F [41H-
46H]) ), except for <CR>. A hex ASCII character specifies 4 bits or
1 nibble of information and is used in high/low pairs to specify a
complete byte of information. Received ASCII nulls (00H), spaces
(20H), and line feeds (0AH) are ignored and are not included in
the byte count.
Command bytes have the following values:
<CR> REQUIRED carriage return character (0DH)
<Adr Hi> 0-F, high nibble of Performer switch 1 address
<Adr Lo> 0-F, low nibble of Performer switch 1 address
<Len Hi> 0-F, high nibble of byte count for <Data>
<Len Lo> 0-F, low nibble of byte count. Count must not
exceed 251 (FBH).
<Data> 0-9, A-Z. Zero or more command strings (see
Command Strings). Number of <Data> characters
is <Len>
If the <Adr Hi> <Adr Lo> value is different from the value set at
Performer switch S1, the command and all subsequent characters
are ignored by the Performer until a new message is initiated
using a carriage return. The carriage return purges previously
received data, and must start each command line.