/* Name: usbdrvasm.S
 * Project: AVR USB driver
 * Author: Christian Starkjohann
 * Creation Date: 2007-06-13
 * Tabsize: 4
 * Copyright: (c) 2007 by OBJECTIVE DEVELOPMENT Software GmbH
 * License: GNU GPL v2 (see License.txt) or proprietary (CommercialLicense.txt)
 * Revision: $Id$
 */

/*
General Description:
This module is the assembler part of the USB driver. This file contains
general code (preprocessor acrobatics and CRC computation) and then includes
the file appropriate for the given clock rate.
*/

#include "iarcompat.h"
#ifndef __IAR_SYSTEMS_ASM__
    /* configs for io.h */
#   define __SFR_OFFSET 0
#   define _VECTOR(N)   __vector_ ## N   /* io.h does not define this for asm */
#   include <avr/io.h> /* for CPU I/O register definitions and vectors */
#   define macro    .macro  /* GNU Assembler macro definition */
#   define endm     .endm   /* End of GNU Assembler macro definition */
#endif  /* __IAR_SYSTEMS_ASM__ */
#include "usbdrv.h" /* for common defs */

/* register names */
#define x1      r16
#define x2      r17
#define shift   r18
#define cnt     r19
#define x3      r20
#define x4      r21
#define bitcnt  r22
#define phase   x4
#define leap    x4

/* Some assembler dependent definitions and declarations: */

#ifdef __IAR_SYSTEMS_ASM__

#   define nop2     rjmp    $+2 /* jump to next instruction */
#   define XL       r26
#   define XH       r27
#   define YL       r28
#   define YH       r29
#   define ZL       r30
#   define ZH       r31
#   define lo8(x)   LOW(x)
#   define hi8(x)   (((x)>>8) & 0xff)   /* not HIGH to allow XLINK to make a proper range check */

    extern  usbRxBuf, usbDeviceAddr, usbNewDeviceAddr, usbInputBufOffset
    extern  usbCurrentTok, usbRxLen, usbRxToken, usbTxLen
    extern  usbTxBuf, usbMsgLen, usbTxLen1, usbTxBuf1, usbTxLen3, usbTxBuf3
#   if USB_COUNT_SOF
        extern usbSofCount
#   endif
    public  usbCrc16
    public  usbCrc16Append

    COMMON  INTVEC
#   ifndef USB_INTR_VECTOR
        ORG     INT0_vect
#   else /* USB_INTR_VECTOR */
        ORG     USB_INTR_VECTOR
#       undef   USB_INTR_VECTOR
#   endif /* USB_INTR_VECTOR */
#   define  USB_INTR_VECTOR usbInterruptHandler
    rjmp    USB_INTR_VECTOR
    RSEG    CODE

#else /* __IAR_SYSTEMS_ASM__ */

#   define nop2     rjmp    .+0 /* jump to next instruction */

#   ifndef USB_INTR_VECTOR /* default to hardware interrupt INT0 */
#       define USB_INTR_VECTOR  SIG_INTERRUPT0
#   endif
    .text
    .global USB_INTR_VECTOR
    .type   USB_INTR_VECTOR, @function
    .global usbCrc16
    .global usbCrc16Append
#endif /* __IAR_SYSTEMS_ASM__ */


#if USB_INTR_PENDING < 0x40 /* This is an I/O address, use in and out */
#   define  USB_LOAD_PENDING(reg)   in reg, USB_INTR_PENDING
#   define  USB_STORE_PENDING(reg)  out USB_INTR_PENDING, reg
#else   /* It's a memory address, use lds and sts */
#   define  USB_LOAD_PENDING(reg)   lds reg, USB_INTR_PENDING
#   define  USB_STORE_PENDING(reg)  sts USB_INTR_PENDING, reg
#endif


;----------------------------------------------------------------------------
; Utility functions
;----------------------------------------------------------------------------

#ifdef __IAR_SYSTEMS_ASM__
/* Register assignments for usbCrc16 on IAR cc */
/* Calling conventions on IAR:
 * First parameter passed in r16/r17, second in r18/r19 and so on.
 * Callee must preserve r4-r15, r24-r29 (r28/r29 is frame pointer)
 * Result is passed in r16/r17
 * In case of the "tiny" memory model, pointers are only 8 bit with no
 * padding. We therefore pass argument 1 as "16 bit unsigned".
 */
RTMODEL "__rt_version", "3"
/* The line above will generate an error if cc calling conventions change.
 * The value "3" above is valid for IAR 4.10B/W32
 */
#   define argLen   r18 /* argument 2 */
#   define argPtrL  r16 /* argument 1 */
#   define argPtrH  r17 /* argument 1 */

#   define resCrcL  r16 /* result */
#   define resCrcH  r17 /* result */

#   define ptrL     ZL
#   define ptrH     ZH
#   define ptr      Z
#   define byte     r22
#   define bitCnt   r19
#   define polyL    r20
#   define polyH    r21
#   define scratch  r23

#else  /* __IAR_SYSTEMS_ASM__ */ 
/* Register assignments for usbCrc16 on gcc */
/* Calling conventions on gcc:
 * First parameter passed in r24/r25, second in r22/23 and so on.
 * Callee must preserve r1-r17, r28/r29
 * Result is passed in r24/r25
 */
#   define argLen   r22 /* argument 2 */
#   define argPtrL  r24 /* argument 1 */
#   define argPtrH  r25 /* argument 1 */

#   define resCrcL  r24 /* result */
#   define resCrcH  r25 /* result */

#   define ptrL     XL
#   define ptrH     XH
#   define ptr      x
#   define byte     r18
#   define bitCnt   r19
#   define polyL    r20
#   define polyH    r21
#   define scratch  r23

#endif

; extern unsigned usbCrc16(unsigned char *data, unsigned char len);
; data: r24/25
; len: r22
; temp variables:
;   r18: data byte
;   r19: bit counter
;   r20/21: polynomial
;   r23: scratch
;   r24/25: crc-sum
;   r26/27=X: ptr
usbCrc16:
    mov     ptrL, argPtrL
    mov     ptrH, argPtrH
    ldi     resCrcL, 0
    ldi     resCrcH, 0
    ldi     polyL, lo8(0xa001)
    ldi     polyH, hi8(0xa001)
    com     argLen      ; argLen = -argLen - 1
crcByteLoop:
    subi    argLen, -1
    brcc    crcReady    ; modified loop to ensure that carry is set below
    ld      byte, ptr+
    ldi     bitCnt, -8  ; strange loop counter to ensure that carry is set where we need it
    eor     resCrcL, byte
crcBitLoop:
    ror     resCrcH     ; carry is always set here
    ror     resCrcL
    brcs    crcNoXor
    eor     resCrcL, polyL
    eor     resCrcH, polyH
crcNoXor:
    subi    bitCnt, -1
    brcs    crcBitLoop
    rjmp    crcByteLoop
crcReady:
    ret
; Thanks to Reimar Doeffinger for optimizing this CRC routine!


; extern unsigned usbCrc16Append(unsigned char *data, unsigned char len);
usbCrc16Append:
    rcall   usbCrc16
    st      ptr+, resCrcL
    st      ptr+, resCrcH
    ret


;----------------------------------------------------------------------------
; Now include the clock rate specific code
;----------------------------------------------------------------------------

#ifndef USB_CFG_CLOCK_KHZ
#   define USB_CFG_CLOCK_KHZ 12000
#endif

#if USB_CFG_CLOCK_KHZ == 12000
#   include "usbdrvasm12.inc"
#elif USB_CFG_CLOCK_KHZ == 15000
#   include "usbdrvasm15.inc"
#elif USB_CFG_CLOCK_KHZ == 16000
#   include "usbdrvasm16.inc"
#elif USB_CFG_CLOCK_KHZ == 16500
#   include "usbdrvasm165.inc"
#else
#   error "USB_CFG_CLOCK_KHZ is not one of the supported rates!"
#endif
