WinSystems PCM-AIO, Operation Manual, Page: 14 / 43

2.12
Output Coding
IN PUT VOLT AGE RANGE COD ING
UNI PO LAR STRAIGHT BI NARY
0 TO +5V MSB LSB
+FS 5.0000 1111 1111 1111
+FS- 1LSB 4.9988 1111 1111 1110
+1LSB 0.0012 0000 0000 0001
ZERO 0.0000 0000 0000 0000
BI PO LAR OFF SET BI NARY
+/- 2.5V MSB LSB
+FS +2.5000 0111 1111 1111
+FS-1 +2.4988 0111 1111 1110
+1LSB +0.0012 0000 0000 0001
ZERO 0.0000 0000 0000 0000
-1LSB -0.0012 1111 1111 1111
-FS-1LSB -2.4988 1000 0000 0001
-FS -2.5000 1000 0000 0000
2.13
A/D SOFTWARE EXAMPLES
The fol low ing gives an ex am ple of an 8088/8086 as sem bly lan guage rou tine that will in -
ter face to the PCM- AIO in syn chro nous polled mode for a 0 to 5 VDC, uni po lar in put range.
mov dx,BASE_PORT ;Set PC/104 Base I/O Ad dress
mov al,0 ;Chan 0, Sin gle Ended, Uni po lar
out dx,al ;Start Con ver sion
add dx,4 ;Point to Status Reg is ter
wait: in al,dx ;Read Status Bit
test al,80H ;See if Con ver sion Fin ished
jne wait ;If Not, Try Again
mov dx,BASE_PORT ;Point to Low data Byte
in al,dx ;Read Low Data Byte
mov bl,al ;Save Low Byte
inc dx ;Point to High Byte
in al,dx ;Read High Byte
mov bh,al ;Com bine with Low Byte
and BX,0FFFH ;BX=Con ver sion Data
The fol low ing pro gram gives an ex am ple of a C pro gram for per form ing A/D con ver sions
with the PCM- AIO.
Page 2-6 OPERATIONS MANUAL PCM-AIO 980723
WinSystems - "The Embedded Systems Authority"