Microchip Technology AN908, Using Manual

Page: 45 / 76

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2004 Microchip Technology Inc. DS00908A-page 45
AN908
;Parameters:
; Input arguments None
;
; Return:
; Void
;
; SFR Settings required None
;
; Support routines required: None
;
; Local Stack usage: 3
;
; Registers modified: None
;
; Timing: About 29 instruction cycles (if new iDeltaCnt produced)
;
;=====================================================
; Equivalent C code
; {
; register short Pos, Delta;
;
; Pos = POSCNT;
;
; Delta = Pos - EncoderParm.iPrevCnt;
; EncoderParm.iPrevCnt = Pos;
;
; if( iDelta >= 0 )
; {
; // Delta > 0 either because
; // 1) vel is > 0 or
; // 2) Vel < 0 and encoder wrapped around
;
; if( Delta >= EncoderParm.iCntsPerRev/2 )
; {
; // Delta >= EncoderParm.iCntsPerRev/2 => Neg speed, wrapped around
;
; Delta -= EncoderParm.iCntsPerRev;
; }
; }
; else
; {
; // Delta < 0 either because
; // 1) vel is < 0 or
; // 2) Vel > 0 and wrapped around
;;
; if( Delta < -EncoderParm.iCntsPerRev/2 )
; {
; // Delta < -EncoderParm.iCntsPerRev/2 => Pos vel, wrapped around
;
; Delta += EncoderParm.iCntsPerRev;
; }
; }
;
; EncoderParm.iAc= Delta;
;
; EncoderParm.iVelCntDwn--;
; if(EncoderParm.iVelCntDwn)
; return;
;
; iVelCntDwn = iIrpPerCalc;
; qVelMech = qKvel * iAccumCnt * 2^Nvel;
; EncoderParm.iAccumCnt = 0;
;}