Link Address Bytes; Result 1 And Result 2 Bytes; General Notes - Lexicon MPX-1 Technical Manual

GENERAL PURPOSE PARAMETER BYTES 0 through 8
These bytes are used to send parameters to the MPX along with the command.
The parameter(s) sent vary with the command. Only the block move com~ands use
all nine bytes, and they would contain the starting, ending and destination
addresses for the block move (3 bytes each). Sometimes only a few bytes are
used and sometimes none are used at all. The exact usage of these bytes is
detailed in each individual command description.
LINK ADDRESS BYTES
These three bytes are a pointer to the place at which the next command line
is resident in the system memory. When not executing multiple commands (CONT
bit
=
0), this address would normally point to the beginning of the same
command. When executing a sequence of commands, this address would point to the
address of the next command.
The address is stored low byte first and is a full 24 bit address.
The initial link address is 50 hex, but the NOP instruction may be used to
change the link address to any other system address.
Note that the link address is read only once and at the start of each
command, not at the end. This means that the command itself may modify the link
address, but it will only affect the following command (not the where the next
command will be fetched). The main system CPU should not modify the current
link address unless the MPX is not active.
RESULT 1 AND RESULT 2 BYTES
"'-,
Sometimes it is desirable to have the MPX return parameters to the caller,
and that is the purpose of these two bytes. Only two of the built-in commands
return data to these locations, but user generated commands should use these
bytes for that purpose as well.
GENERAL NOTES
Commands are assumed to be resident on 16 byte boundaries ie: SOR, 60R,
180R, etc.
The only bytes in the command line that the MPX modifies are the status
indication and result bytes. All others are left intact.
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