Excerpts for 116B (224KB)

Addressing Capabilities
After a put operation, the put address register points to the last item placed in the queue; the
unchanged get address register points to the last item removed from the queue. After a get
operation, the get address register points to the last item placed in the queue.
.
PUT – (An)
LOW MEMORY
(FREE)
LAST PUT
GET – (Am)
NEXT GET
LAST GET (FREE)
HIGH MEMORY
To implement the queue as a circular buffer, the get or put operation should be performed
first. Then the relevant address register should be checked and adjusted, if necessary.
Adding the buffer length (in bytes) to the address register contents adjusts the address
register.
2-30 M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL MOTOROLA