di2874l1.txt
;******************************************************************************************
; 
; LISTING 1 - MBASIC LISTING FOR MOTION-CONTROL ADAPTER
;
; "Unidirectional counters accumulate bidirectional pulses," EDN, April 11, 2002, pg 72
;
;******************************************************************************************
DEFINT I
IOADD = &H300: ‘   BASE ADDRESS FOR MOCONT CARD
IC0 = IOADD:  IC1 = IC0 + 1: IC2 = IC0 + 2: ICS = IC0 + 3: ‘   8254 COUNTER ADDRESSES
OUT ICS, &H70: OUT ICS, &HB0: ‘  SETUP CW/CCW COUNTERS IN C1 AND C2

OUT ICS, &HDC: ‘  LATCH CW/CCW
I1L = INP(IC1):  ICW = INP(IC1)
I2L = INP(IC2):  ICCW = INP(IC2)
OUT  IC1,  I1L:  OUT  IC1,  ICW: ‘  …INITIALIZE CW/CCW COUNTERS
OUT  IC2,  I2L:  OUT  IC2,  ICCW
OFFSET = I1L – I2L + 256! * (ICW –ICCW)

CLS : PRINT TAB(20); “MOTION-CONTROL ADAPTER DEMO”
PRINT TAB(18); “W.S. WOODWARD…March 16, 1990”

AROUND:

OUT  ICS,  &HDC:  ‘  LATCH  CW/CCW
I1L = INP(IC1):  I1M = INP(IC1):  IF  I1M > ICW  THEN  OFFSET = OFFSET + 65536
ICW = I1M
I2L = INP(IC2):  I2M = INP(IC2):  IF  I2M > ICCW  THEN OFFSET = OFFSET – 65536
ICCW = I2M
LOCATE  3, 10:  PRINT  I1L – I2L + 256! * (I1M – I2M) –OFFSET

GOTO  AROUND