Propeller Manual

Table Of Contents

PAR – Spin Language Reference

Page 178 · Propeller Manual v1.1

PAR

((PUB ┆ PRI))

PAR

Returns: Address value passed during launch of assembly code with COGINIT or COGNEW.

Explanation

The

PAR register contains the address value passed into the Parameter field of a COGINIT or

COGNEW command; see COGINIT, page 76 and COGNEW, page 78. The PAR register’s contents are

used by Propeller Assembly code to locate and operate on memory shared between Spin code

and assembly code.

Since the PAR register is intended to contain an address upon cog launch, the value stored into

it via

COGINIT and T COGNEW is limited to 14 bits: a 16-bit word with the lower two bits cleared

to zero.

Using PAR

PAR is affected by Spin code and is used by assembly code as a memory pointer mechanism to

point to shared main memory between the two. Either the

COGINIT or T COGNEW command, when

launching Propeller Assembly into a cog, affects the

PAR register. For example:

VAR

long Shared 'Shared variable (Spin & Assy)

PUB Main | Temp

cognew(@Process, @Shared) 'Launch assy, pass Shared addr

repeat

DAT

org 0

Process mov Mem, PAR 'Retrieve shared memory addr

:loop <do something>

wrlong ValReg, Mem 'Move ValReg value to Shared

jmp #:loop

Mem res 1

ValReg res 1