LP-AM243: PRU CRC16/32 Module base code

Hi Chen,

1. As per TRM, R25 should be written 4 bytes at a time

There is some info missing in TRM please find below.  It will be updated in next revision.

2. PRU ICSS is based on little endian architecture, so the input data should be given as 0413

3. Also For CRC16 mode, SW can read CRC_DATA_32_BFLIP[31:16] to get the correct bit order.

Please find the working code below.

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;************************************************************************************
;   File:     main.asm
;
;   Brief:    Template asm file example
;************************************************************************************

; CCS/makefile specific settings
    .retain     ; Required for building .out with assembly file
    .retainrefs ; Required for building .out with assembly file

    .global     main
    .sect       ".text"

;************************************* includes *************************************
; icss_constant_defines.inc: Defines symbols corresponding to Constant Table Entries
    .include "icss_constant_defines.inc"

    .asg	R2,	TEMP_REG
DATA16  .set    0x0413	;ASCII equivalent for "21"
CRC_XID  .set	0x1
;********
;* MAIN *
;********

main:

init:
;----------------------------------------------------------------------------
;   Clear the register space
;   Before begining with the application, make sure all the registers are set
;   to 0. PRU has 32 - 4 byte registers: R0 to R31, with R30 and R31 being special
;   registers for output and input respectively.
;----------------------------------------------------------------------------

; Give the starting address and number of bytes to clear.
    zero	&r0, 120

; CRC 16
CRC_16:
	ZERO	&R25,	4
	XOUT	CRC_XID,	&R25,	4
	LDI		R29.w0, DATA16   	;Move the data to R29 register
	XOUT 	CRC_XID, &R29.w0, 2		;Moving 2 bytes
    NOP
	XIN 	CRC_XID, &R28, 4 ;Reading  CRC
	XIN 	CRC_XID, &R29, 4
    halt ; end of program