Digital Input/Output Hardware

Basic signed integers

When reading or writing ports that are 16-bits wide, be aware of the following issue using signed integers, as you are forced to do when using Basic:

With some devices, the AUXPORT digital ports are set up as one 16-bit port. When using cbDOut() or DOut(), the digital values are written as a single 16-bit word. Using signed integers, writing values above 0111 1111 1111 1111 (32,767 decimal) can be confusing. The next increment, 1000 0000 0000 0000 has a decimal value of –32,768. Using signed integers, this is the value that you would use for turning on the MSB only. The value for all bits on is –1. Keep this in mind if you are using Basic, since Basic does not supply unsigned integers (values from 0 to 65,536).

To maximize the performance of the digital I/O function calls, refer to the 82C55 data sheet (82C55A.pdf) in the Documents subdirectory where the UL is installed (C:\Program files\Measurement Computing\DAQ by default). You can also refer to the 8536 data sheet, although this document is not installed with the Universal Library.

Digital ports and corresponding bit numbers (82C55-based hardware and emulations)

The following table lists the port numbers and corresponding bit numbers that are set by the digital I/O functions for hardware designed with the 82C55 chip or 82C55 emulation.

cbDConfigPort() port reference	cbDIn(), cbDOut() port reference	Values	cbDBitIn(), cbDBitOut() port reference	Bit Number
FIRSTPORTA	FIRSTPORTA	0-255	FIRSTPORTA	0 to 7
FIRSTPORTB	FIRSTPORTB	0-255	FIRSTPORTA	8 to 15
FIRSTPORTCL	FIRSTPORTCL	0-15	FIRSTPORTA	16 to 19
FIRSTPORTCH	FIRSTPORTCH	0-15	FIRSTPORTA	20 to 23

SECONDPORTA	SECONDPORTA	0-255	FIRSTPORTA	24 to 31
SECONDPORTB	SECONDPORTB	0-255	FIRSTPORTA	32 to 39
SECONDPORTCL	SECONDPORTCL	0-15	FIRSTPORTA	40 to 43
SECONDPORTCH	SECONDPORTCH	0-15	FIRSTPORTA	44 to 47

THIRDPORTA	THIRDPORTA	0-255	FIRSTPORTA	48 to 55
THIRDPORTB	THIRDPORTB	0-255	FIRSTPORTA	56 to 63
THIRDPORTCL	THIRDPORTCL	0-15	FIRSTPORTA	64 to 67
THIRDPORTCH	THIRDPORTCH	0-15	FIRSTPORTA	68 to 71

FOURTHPORTA	FOURTHPORTA	0-255	FIRSTPORTA	72 to 79
FOURTHPORTB	FOURTHPORTB	0-255	FIRSTPORTA	80 to 87
FOURTHPORTCL	FOURTHPORTCL	0-15	FIRSTPORTA	88 to 91
FOURTHPORTCH	FOURTHPORTCH	0-15	FIRSTPORTA	92 to 95

FIFTHPORTA	FIFTHPORTA	0-255	FIRSTPORTA	96 to 103
FIFTHPORTB	FIFTHPORTB	0-255	FIRSTPORTA	104 to 111
FIFTHPORTCL	FIFTHPORTCL	0-15	FIRSTPORTA	112 to 115
FIFTHPORTCH	FIFTHPORTCH	0-15	FIRSTPORTA	116 to 119

SIXTHPORTA	SIXTHPORTA	0-255	FIRSTPORTA	120 to 127
SIXTHPORTB	SIXTHPORTB	0-255	FIRSTPORTA	128 to 135
SIXTHPORTCL	SIXTHPORTCL	0-15	FIRSTPORTA	136 to 139
SIXTHPORTCH	SIXTHPORTCH	0-15	FIRSTPORTA	140 to 143

SEVENTHPORTA	SEVENTHPORTA	0-255	FIRSTPORTA	144 to 151
SEVENTHPORTB	SEVENTHPORTB	0-255	FIRSTPORTA	152 to 159
SEVENTHPORTCL	SEVENTHPORTCL	0-15	FIRSTPORTA	160 to 163
SEVENTHPORTCH	SEVENTHPORTCH	0-15	FIRSTPORTA	164 to 167

EIGHTHPORTA	EIGHTHPORTA	0-255	FIRSTPORTA	168 to 175
EIGHTHPORTB	EIGHTHPORTB	0-255	FIRSTPORTA	176 to 183
EIGHTHPORTCL	EIGHTHPORTCL	0-15	FIRSTPORTA	184 to 187
EIGHTHPORTCH	EIGHTHPORTCH	0-15	FIRSTPORTA	188 to 191

Notes

For devices that support AUXPORT, in general only bit numbers 0 to 7 apply. Refer to board-specific information for details on the number of bits your hardware supports.
For devices that support synchronous I/O scanning, such as the USB-2500 Series, PORTC is configured as one 8-bit port (PORTCH and PORTCL are not supported). Refer to board-specific information for details on which ports are supported by your hardware.