USB Code Test wrtitten in asm

8/13/2019 USB Code Test wrtitten in asm

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;**********************************************************************; *; Filename: USB_Code_test.asm *; Date: 15th April 2006 *; File Version: 1.0 *; *; Author: Ian Stedman *; Company: *; *; *;**********************************************************************; *; Files required: *; *; *; *;**********************************************************************; *; Notes: *; A simple program to test the PIC16F877 to FTDI USB interface. *; It sends 'walking bit codes that are used to verify that there *; Are no stuck bits or solder shorts between pins.; *; *

;**********************************************************************

list p=16f877 ; list directive to define processor#include ; processor specific variable definitions

__CONFIG _LVP_OFF & _CP_OFF & _WDT_OFF & _BODEN_ON & _PWRTE_OFF & _HS_OSC & _WRT_ENABLE_ON & _DEBUG_OFF & _CPD_OFF

; '__CONFIG' directive is used to embed configuration data within .asm file.; The lables following the directive are located in the respective .inc file.; See respective data sheet for additional information on configuration word.

;***** VARIABLE DEFINITIONSw_temp EQU 0x40 ; variable used for context savingstatus_temp EQU 0x42 ; variable used for context savingadcresult EQU 0x44 ; ADC conversion resultusbdatarx EQU 0x46 ; Byte received from USB portusbdatatx EQU 0x48 ; Byte to send via USBcount EQU 0x50temp EQU 0x52time EQU 0x54READBIT EQU 0 ; PORT C Read bit to USBWRITEBIT EQU 1 ; PORT C Write bit to USBTXFULL EQU 2 ; PORT C TX Full input from US

BRXFULL EQU 3 ; PORT C RX Full input from USBINPORT EQU 255 ; Sets an I/O port as all inputsOUTPORT EQU 0 ; Seta an I/O port as all outputs

;**********************************************************************ORG 0x000 ; processor reset vectorclrf PCLATH ; ensure page bits are cleared


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goto main ; go to beginning of program

ORG 0x004 ; interrupt vector locationmovwf w_temp ; save off current W register contentsmovf STATUS,w ; move status register into W registermovwf status_temp ; save off contents of STATUS register

; isr code can go here or be located as a call subroutine elsewhere

movf status_temp,w ; retrieve copy of STATUS registermovwf STATUS ; restore pre-isr STATUS register cont

entsswapf w_temp,fswapf w_temp,w ; restore pre-isr W register contentsretfie ; return from interrupt

main call picinitmainloop call usbrecv

call display

movlw 20movwf timecall delay

; Start of the test code. The idea is to turn on each data bit individually, giving 32 codes for the 8 bit interface

movlw h'00'movwf usbdatatxcall usbsendmovlw h'01'movwf usbdatatxcall usbsendmovlw h'02'movwf usbdatatx

call usbsendmovlw h'03'movwf usbdatatxcall usbsendmovlw h'04'movwf usbdatatxcall usbsendmovlw h'05'movwf usbdatatxcall usbsendmovlw h'06'movwf usbdatatxcall usbsend

movlw h'07'movwf usbdatatxcall usbsendmovlw h'08'movwf usbdatatxcall usbsendmovlw h'09'movwf usbdatatxcall usbsendmovlw h'0A'


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movwf usbdatatxcall usbsendmovlw h'0B'movwf usbdatatxcall usbsendmovlw h'0C'movwf usbdatatxcall usbsendmovlw h'0D'movwf usbdatatxcall usbsendmovlw h'0E'movwf usbdatatxcall usbsendmovlw h'0F'movwf usbdatatxcall usbsendmovlw h'10'movwf usbdatatxcall usbsendmovlw h'20'movwf usbdatatxcall usbsendmovlw h'30'

movwf usbdatatxcall usbsendmovlw h'40'movwf usbdatatxcall usbsendmovlw h'50'movwf usbdatatxcall usbsendmovlw h'60'movwf usbdatatxcall usbsendmovlw h'70'movwf usbdatatx

call usbsendmovlw h'80'movwf usbdatatxcall usbsendmovlw h'90'movwf usbdatatxcall usbsendmovlw h'A0'movwf usbdatatxcall usbsendmovlw h'B0'movwf usbdatatxcall usbsend

movlw h'C0'movwf usbdatatxcall usbsendmovlw h'D0'movwf usbdatatxcall usbsendmovlw h'E0'movwf usbdatatxcall usbsendmovlw h'F0'


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movwf usbdatatxcall usbsendmovlw h'00'movwf usbdatatxcall usbsend

goto mainloop

; remaining code goes here

picinitbanksel OPTION_REGmovlw H'07'movwf OPTION_REG ; Set TMR0 to divide internal cl

ock by 256banksel TRISB

movlw OUTPORT movwf TRISB ;portb [7-0] outputs

movwf TRISA ;porta [7-0] outputsmovlw H'0C' ;setup portc [2-3] inputs [0-1,4

-7] outputsmovwf TRISC

movlw INPORT ;setup portd as inputs for now (USB port)movwf TRISDclrf ADCON1 ;left justified, all inputs a/d

bcf STATUS,RP0 ;bank 0movlw H'FF'movwf PORTC ; Ensure Ouputs are 1 (no read/w

rite)clrf PORTB ; All LEDs off.clrf PORTA

movlw B'01000001' ;Fosc/8 [7-6], A/D ch0 [5-3], a/d on [0] movwf ADCON0

bsf PORTC,6 ; Debug

return

; At the moment a simple function to output the received USB value to the 8 LEDson Port B

displaymovf usbdatarx,W ; Recall received databcf PORTC,7movf usbdatarx,Wmovwf PORTB ; Output it, job done!bsf PORTC,7bsf PORTC,6bsf PORTC,5

return

; A function to check for data received from the USB interface and if present, read it.; USB is on port D, RC0=READ, RC3=RX_Flagusbrecv

btfsc PORTC,RXFULL ; See if RX_flag = 0 which indicates there is data in the FIFO

retlw 0 ; return 0 for no data;If we got here there is data to read. Set PORT D = Input, READ=


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High, wait, READ=Low then read port Dbanksel TRISDmovlw INPORTmovwf TRISD ; PORT D now input, safe to star

t the read access.banksel PORTDbsf PORTC,READBITnopnopbcf PORTC,READBIT ; READ now active LOW so READ po

rt Dnopnopmovf PORTD,Wmovwf usbdatarxbsf PORTC,READBIT ; Set RD = higreturn

; A function to send a byte of information via the USB interface. Checks the TXFflag prior to sending.; USB is on port D, RC1=Write, RC2=TX_Flag; The data to send will be in usbdatatx

usbsend movf PORTC,W ; Read in PORT C for debugbtfsc PORTC,TXFULL ; See if TX_Flag = 0 which indicates OK

to transmit.retlw 0 ; Return with 0 if full

how????;If we get here we can transmit. Set PORT D = output, WRITE=High

, Wait, WRITE=Low then Write Data, Write=Highbanksel TRISDmovlw OUTPORTmovwf TRISD ; PORT D now outputbanksel PORTDbsf PORTC,WRITEBIT ; Make sure WR is high before dat

a output. movf usbdatatx,Wmovwf PORTDnopbcf PORTC,WRITEBIT ; Write now activenopbsf PORTC,WRITEBIT ; All done, WR = high.

; Now tristate the databus, set PORT D to input.banksel TRISDmovlw INPORTmovwf TRISD ; PORT D now inputbanksel PORTD ; Return to page 0nop

return

;*******************************************************************; DELAY Subroutine. This routine provides a 1 second delay. Call for; as long as you want by storing your desired delay in 'time' before; calling.; EXAMPLE; movlw 10 ; The value here determines the time delay in seconds.; movwf time ; Store the value.; call delay ; call the delay routine.


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;

delay call delay1 ; these lines make sure that the 1 second loop executes ntimes.

decfsz timegoto delayreturn ; When time is up, return from subroutine.

delay1 ; The code here initialise the RTCC.bsf STATUS,RP0movlw 0x07 ; For use by RTCC, prescaler was /256 or 0x07movwf OPTION_REG ; dittobcf STATUS,RP0clrf TMR0movlw 0x0e ; Delay time value for 1 secondmovwf count ; store the valuemovwf temp

sloop ; What follows is the actual delay loop for 1 second. btfsc TMR0,5 ; Reset the RTCC, wait for TMR0 bit 5 to go hich

goto jmp1goto sloop

jmp1 clrf TMR0 ; RTCC is cleared so decrement the count & repeat.

decfsz countgoto sloopwlooplo decfsz temp,F

goto wlooploreturn

END ; directive 'end of program'

USB Code Test wrtitten in asm

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