MA3690/1/3
CONTINUOUS OPERATION
The continuous message table
operation mode can be achieved by
ensuring that at the end of a message the
HALTREQN line is high. Thus, assuming
that the message has executed correctly,
the terminal will generate a signal to
increment the external address counter
(INCADRN) and continue to the next
instruction. If, however there has been an
interrupt generated (IRQN active) the
terminal will halt in the HALTEDN state
until specifically requested to continue.
Note that no address increment will take
place. To continue execution the
HALTREQN line should be taken low to
high for the appropriate time.
Continuous table driven operation
results in an intermessage gap of 20us.
Figure 1 shows the instruction fetch
and execute cycle.
Has
HALTREQ
gone low to
high ?
YES
Set
HALTED
high
NO
Fetch Instruction
Message
Command
Error ?
NO
Execute
Instruction
YES
YES
Retry
Required ?
NO
Retry
Count = 0 ?
NO
Decrement
Retry Count
YES
Output
Report Word
YES
INT.
Required ?
NO
Pulse
IRQ
Increment
Instruction Address
SET
HALTED
low
YES
HALTREQ
=0?
NO
Figure 1: BC Instruction Fetch and Execute Cycle
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DYNEX [ Dynex Semiconductor ]
