Propeller Manual

3: Assembly Language Reference
flag, and to write, or not write, the instruction’s result value to the destination
register, respectively. See Effects on page 291 for more information.
Since every instruction can include these three optional fields (Label, Condition, and Effects),
for simplicity those common fields are intentionally left out of the instruction’s syntax
description.
So, when you read a syntax description such as this:
WAITCNT Target, 〈#〉 Delta
...remember that the true syntax is this:
〈Label〉 〈Condition〉 WAITCNT Target, 〈#〉 Delta 〈Effects〉
This rule applies only to Propeller Assembly instructions; it does not apply to Propeller
Assembly directives.
Syntax declarations always give descriptive names to the instruction’s operands, such as
WAITCNT’s Target and Delta operands in the example above. The detailed descriptions refer to
operands by these names, however, the opcode tables and truth tables always use the generic
names (D, DEST, Destination, and S, SRC, Source) to refer to the instruction’s bits that store
the respective values.
Opcodes and Opcode Tables
Most syntax definitions include an opcode table similar to the one below. This table lists the
instruction’s 32-bit opcode, outputs and number of clock cycles.
The opcode table’s first column contains the Propeller Assembly Instruction opcode,
consisting of the following fields:
•
INSTR (bits 31:26) - Indicates the instruction being executed.
•
ZCRI (bits 25:22) - Indicates instruction’s effect status and SRC field meaning.
•
CON (bits 21:18) - Indicates the condition in which to execute the instruction.
•
DEST (bits 17:9) - Contains the destination register address.
•
SRC (bits 8:0) - Contains the source register address or 9-bit literal value.
The bits of the
ZCRI field each contain a 1 or 0 to indicate whether or not the ‘Z’ flag, ‘C’ flag,
and ‘R’esult should be written, and whether or not the
SRC field contains an ‘I'mmediate value
(rather than a register address). The Z and C bits of the
ZCRI field are clear (0) by default and
Propeller Manual v1.1 · Page 251