Motorola DSP56000 Manual page 566

3. Evaluate the "ap'' term using Table A-14.
According to Table A-14, the term "ap'' depends upon where the referenced P memory
location is located in the DSP56K memory space. External memory accesses require
additional oscillator clock cycles according to the number of wait states programmed into
the DSP56K bus control register (BCR). Thus, assuming that the 16-bit bus control regis-
ter contains the value $0012, external P memory accesses require wp=1 w ait state or
additional oscillator clock cycles. For this example, the P memory reference is assumed
to be an internal reference. This means that the return address ($0100) pulled from the
system stack by the RTI instruction is in internal P memory. Thus, according to Table A-
14, the RTI instruction will use the value ap=0 additional oscillator clock cycles.
4. Compute final results.
Thus, based upon the assumptions given for Table A-6 and those listed in the problem
statement for Example 3, the instruction
will require
and will execute in
A - 300
INSTRUCTION TIMING
RTI
1 instruction program word
(4+rx)
= (4+(2 ∗ ap))
= (4+(2 ∗ 0))
= 4 oscillator clock cycles
INSTRUCTION SET DETAILS MOTOROLA