Table 3-5 Instructions With Program Memory; Arguments - Motorola DSP56600 Manual

Program Control
PC Relative Instructions
3-14
In absolute addressing, the argument is the numerical value of the
address. In PC relative addressing, the argument is the
displacement of the address relative to the PC. For both absolute
and PC addressing, the address argument could be specified in one
of four ways:
1. explicit, as part of the 1-word opcode (restricted to short

arguments),

2. explicit, as a second program word ,
3. stored in a register , or,
4. indirect, stored in the memory and accessed by one of the
addressing modes <ea>.
A full list of instructions requiring a program location argument
and the possible addressing modes for each is summarized in
Table 3-5. The shaded sections in the table indicate instructions that
use PC relative arguments.
Note: The instructions LRA (load PC relative address) and LUA
(load effective address) can be used to calculate and load PC
relative address or an effective address, respectively. LRA is
a very efficient and common way for a program to monitor
directly the PC value during runtime.
Note: The DSP56600 does not include the complete set of
PC-Relative instructions like the DSP56300. There is also a
way to disable all the PC-Relative instructions on the
DSP56600 by setting a special mode bit, the PCD (PC relative
logic Disable) which is Bit 5 in the Operating Mode Register
(OMR). For details please see the DSP56600 Family Manual .
Table 3-5 Instructions with Program Memory Arguments
Address
Function
Argument
unconditional
destination
jump
jump on CCR
destination
condition
Optimizing DSP56300/DSP56600 Applications
The Address Argument
Mnemonic
Encoded in the
opcode
(total 1 w)
JMP addr < 4096
BRA –257 <
disp < 256
Jcc address <
4096
Bcc –257 <
disp < 256
2nd Register Data
word Memory
<ea>
+ – +
+ + –
+ – +
+ + –
MOTOROLA