Measurement Computing Data Acquisition Systems rev.10.4 - Manual (Page 266)

Local I/O
Those devices which support the P2 port have built-in Intel 8255C chips which can be used as general purpose I/O.
The 8255C has 3 configurable DIO ports (PortA, PortB, PortC). These ports are 8-bit ports which can be
individually programmed as either input or output ports. All three of the local P2 ports can be written
asynchronously using the daqIOWrite function.
Additionally, there is a 16-bit Digital port on P3 of the main unit.* If P3 is supported, the DaqBook/100 Series,
DaqBook/200 Series, Daq PC-Card, ISA-type DaqBoard, DaqBook/2000 Series, DaqBoard/2000 Series*, and cPCI
DaqBoard/2000c Series devices allow this port to be used as a high speed digital port which can be scanned
synchronously along with other analog channels in a acquisition.
Some devices, such as the DaqBook/2000 Series, DaqBoard/2000 Series [and 2000c Series] products, can also
access this port asynchronously as a general purpose DIO port. If using the DaqBoard/2000 Series [or 2000c Series]
products, the daqIORead function can be used to read this port asynchronously.
* Note : P3 for DaqBoard/2000 Series boards is obtained by connecting an appropriate DBK200 Series board to the DaqBoard/2000
Series board’s P4 connector, via cable.
Expansion I/O
There are several options that allow for DIO expansion. These expansion options, referred to as the DBK20 Series
cards, operate off of the main unit’s P2 port and can be accesssed asynchronously. The expansion cards vary in
number of DIO, connectivity, and isolation characteristics. Refer to the DBK Cards and Options User’s Manual
(p/n 457-0905) in regard to the specifics of your particular DBK20 Series card.
When using a DBK20 Series expansion card on P2, the Local P2 port becomes inaccessible.
The following table describes typical port settings. “n” is the expansion card’s position in a system. In a three
card system the first card would have n = 0, the second card n = 1, and the third card n = 2.
Digital I/O Port devType devPort whichDevice whichExpPort
P2 Local DIO ( one 8255 – three 8-bit DIO banks)
P2 Local 8255 Port A
(P2 pins 30-37)
DiodtP2Local8 DiodpP2Local8 Diodp8255A DioepP2
P2 Local 8255 Port B
(P2 pins 3-10) DiodtP2Local8 DiodpP2Local8 Diodp8255B DioepP2
P2 Local 8255 Port C
(P2 pins 22-28) DiodtP2Local8 DiodpP2Local8 Diodp8255C DioepP2
P3 Local DIO/HS Digital IO (one 16-bit DIO bank)
P3 Local 16-bit Port*
(P3 pins 3-10, 22-29)
DiodtP3LocalDig16 DiodpP3LocalDig16 DiodpP3LocalDig16 DioepP3
P2 Expansion DIO with DBK20/21 (dual 8255’s – six 8-bit DIO banks) “n” is the expansion card’s position in a system.
P2 Exp 8255-0 Port A
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255A DioepP2
P2 Exp 8255-0 Port B
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255B DioepP2
P2 Exp 8255-0 Port C
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255C DioepP2
P2 Exp 8255-1 Port A
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255A + 4 DioepP2
P2 Exp 8255-1 Port B
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255B + 4 DioepP2
P2 Exp 8255-1 Port C
(see DBK20/21 doc) DiodtExp8255 DiodpP2Exp8 (nx8) + Diodp8255C + 4
( see example)
DioepP2
P2 Expansion DIO with DBK23 ( three 8-bit DIO banks) “n” is the expansion card’s position in a system.
P2 Exp DBK23 Port A DiodtDbk23 DiodpP2Exp8 (nx4) + DiodpDbk23A DioepP2
P2 Exp DBK23 Port B DiodtDbk23 DiodpP2Exp8 (nx4) + DiodpDbk23B DioepP2
P2 Exp DBK23 Port C DiodtDbk23 DiodpP2Exp8 (nx4) + DiodpDbk23C DioepP2
P2 Expansion DIO with DBK24 ( three 8-bit DIO banks)
P2 Exp DBK24 Port A
DiodtDbk24 DiodpP2Exp8 (nx4) + DiodpDbk24A DioepP2
P2 Exp DBK24 Port B DiodtDbk24 DiodpP2Exp8 (nx4) + DiodpDbk24B DioepP2
P2 Exp DBK24 Port C DiodtDbk24 DiodpP2Exp8 (nx4) + DiodpDbk24C DioepP2
P2 Expansion DIO with DBK25 (one 8-bit DIO bank) “n” is the expansion card’s position in a system.
P2 Exp DBK25 Port DiodtDbk25 DiodpP2Exp8 n + DiodpDbk25 DioepP2
WBK17
WBK17 Digital Output
DiodtWbk17 DiodpWbk17_8Bit First channel on unit (9, 17, 25 …) DioeP1
4.5-36 Daq API Command Reference
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Programmer’s Manual