Using The Instruction Summary Tables; Table 6-16 Data Alu Registers - Motorola DSP56800 Manual

Instruction Set Introduction
Register Field Registers in This Field
FDD
F1DD
DD
F
F1
6.6.2

Using the Instruction Summary Tables

This section contains helpful information on using the summary tables. It contains some notation used
within the tables.
The register field notation is found in Section 6.6.1, "Register Field Notation."
Some additional notation to be considered is found in the instruction summary tables when allowed
registers for multiplications are specified (Table 6-22 on page 6-20). In these tables, the following entry is
found:
(+)Y0,X0,FDD
The notation (+) in this entry indicates that an optional + or - sign can be specified before the input register
combination. If a - is specified, the multiplication result is inverted. This allows each of the following
examples to be valid DSP56800 instructions:
MAC X0,Y0,A; A + X0*Y0 -> A
MAC +X0,Y0,A; A + X0*Y0 -> A
MAC -X0,Y0,A; A - (X0*Y0) -> A
As an example, Table 6-35 on page 6-30 shows all registers and addressing modes that are allowed when
performing a dual read instruction, one of the DSP56800's parallel move instructions. The instructions
shown in Example 6-3 are allowed.
MOVE
MACR X0,Y1,A
ADD Y0,B
The instruction in Example 6-4 is not allowed:
ADD X0,Y1,A
6-16
Table 6-16. Data ALU Registers
A, B Five data ALU registers—two 36-bit accumulators and three 16-bit
X0, Y0, Y1 data registers accessible during data ALU operations
Contains the contents of the F and DD register fields
A1, B1 Five data ALU registers—two 16-bit MSP portions of the
X0, Y0, Y1 accumulators and three 16-bit data registers accessible during data
ALU operations
X0, Y0, Y1 Three 16-bit data registers
A, B Two 36-bit accumulators accessible during parallel move instruc-
tions and some data ALU operations
A1, B1 The 16-bit MSP portion of two accumulators accessible as source
operands in parallel move instructions
Example 6-3. Valid Instructions
X:(R0)+,Y0
X:(R1)+N,Y1
X:(R1)+N,Y0
Example 6-4. Invalid Instruction
X:(R2)-,X0
DSP56800 Family Manual
Comments
X:(R3)+,X0
X:(R3)-,X0
X:(R3)+,X0
X:(R3)+N,Y0