Register Addressing; Word Count; Peripheral Addressing - Motorola DSP56600 Manual

7.2.5

Register Addressing

The register addressing can also be used to decrease the total cycle
count. The next example is an implementation of a jump table that
uses register addressing. The code is used when exiting reset to
jump to a location that corresponds to the specific mode that was
chosen at power up:
org
move
and
move
move
move
jmp
j_table
dc
dc
dc
dc
dc
dc
dc
dc
7.2.6

Word Count

Some instructions have single word versions that should be used
when possible. It is advisable to consult the Family Manuals for
details on the word count of the various instructions.
7.3

PERIPHERAL ADDRESSING

The on-chip peripherals have special addressing modes. Moving
data to/from an on-chip peripheral can be done by a MOVEP
instruction, where the address of the peripheral is defined by very
few address bits as part of the opcode.
The use of MOVEP usually does not save execution time, but makes
it possible to put two MOVEP instructions in an interrupt vector,
instead of only one if a long absolute addressing mode is used.
MOTOROLA Optimizing DSP56300/DSP56600 Applications
p:$400
omr,a
#<$7,a
#j_table,r0
a,n0
p:(r0+n0),r0
(r0)
;jump table starting address
1ST_R ;If MC:MB:MA=000, goto 1st routine
2ND_R ;If MC:MB:MA=001, goto 2nd routine
3RD_R ;If MC:MB:MA=010, goto 3rd routine
4TH_R ;If MC:MB:MA=011, goto 4th routine
5TH_R ;If MC:MB:MA=100, goto 5th routine
6TH_R ;If MC:MB:MA=101, goto 6th routine
7TH_R ;If MC:MB:MA=110, goto 7th routine
8TH_R ;If MC:MB:MA=111, goto 8th routine
Compact Opcode Use
Peripheral Addressing
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