Instruction Summary Tables - Motorola DSP56800 Manual

Consulting the information in Table 6-35 on page 6-30 shows that this instruction is not valid for each of
the following reasons:
• The only operands accepted for ADD or SUB are X0,F, Y1,F, Y0,F, A,B, or B,A, where F is either
the A or B accumulator register. Thus, X0,Y1,A is an invalid entry.
• The pointer R2 is not allowed for the first memory read.
• The post-decrement addressing mode is not available for the first memory read.
• The X0 register may not be a destination for the first memory read because it is not listed in the
Destination 1 column.
• The post-update by N addressing mode is not allowed for the second memory read. The second
memory read is always identified as the memory move that uses R3 in instructions with two
memory moves. For the second memory read, only the post-increment and post-decrement
addressing modes are allowed.
• The Y0 register may not be a destination for the second memory read because it is not listed in the
Destination 2 column.
6.6.3

Instruction Summary Tables

A summary of the entire DSP56800 instruction set is presented in this section in tabular form. In these
tables, Table 6-17 on page 6-18 through Table 6-35 on page 6-30, the instructions are broken into several
different categories and then listed alphabetically.
The tables specify the operation, operands, and any relevant comments. There are separate fields for
sources and destinations of move instructions. There are also two additional fields:
• C—Time required to execute the instruction
• W—Number of program words occupied by the instruction
Instruction execution times are measured in oscillator clock cycles. This should not be confused with
instruction cycles, which comprise the timing granularity of the DSP56800 execution units. Each
instruction cycle is equivalent to two oscillator clock cycles. The numbers given for instruction times
assume that internal memory—or external memory that requires no wait states—is used.
All parallel move instructions are located in the last two tables in this section:
• Table 6-34 on page 6-29
• Table 6-35 on page 6-30
Instruction Set Introduction
DSP56800 Instruction Set Summary
6-17