Lexicon MPX-1 User Manual

ATTN RESPONSE
When an ATTN occurs. first the interrupt output is cleared, the ATTN inter-
rupt input is masked and the last link address is copied into CURRENT. Then 16
bytes are read from the system memory (pointed to by CURRENT) into a buffer
called CMNDBUF. The opcode byte is read from the buffer and decoded. A call is
then made to the address pointed to by the lower 5 bits of the opcode. The
opcode is first checked to see if it is the same as the ATTN jump address. If
it is. a NOP command is substituted instead. Control has now been transfered to
the actual command routine. When the command is done executing, all it need do
is a RET instruction to get back to the main interpreter loop.
When a command is finished. the program branches to CHECK. This routine
checks to see if the CONT bit was set in that opcode. If it was, a jump occurs
to the ATTN routine and the next command is executed. If the CONT bit is not
set, the INT bit is checked. If it is set, the status byte is set to FFH and
the SOD interrupt output is set and the MPX then waits for the next ATTN. If
the INT bit is not set, the status byte is set to FFH and the MPX waits for the
next ATTN.
GENERAL PURPOSE SUBROUTINES

Lexicon MPX-1 Specifications

General

Brand	Lexicon
Model	MPX-1
Category	Recording Equipment
Language	English