104-DIO-48S and 104-DIO-24S
Change-Of-State Detecting Digital I/O Cards
Features
- 48 or 24 parallel lines of 82C55 digital I/O with tristate buffers prevent unintended control of external equipment
- IRQ on input change of state (COS) eliminates the need for constant polling
- High sink/source current 64mA/32mA
- I/O pulled up to 5V for contact monitoring
- Compatible with Opto-22 and other industry standard I/O racks

- 82C54 with three 16-bit counter/timers for event counting, frequency output, pulse width and frequency measurement
- 0 to 70°C and -40 to +85°C versions available
- Economy version without COS feature
- Pull-down resistors on I/O lines
Digital I/O
The circuits use an 82C55A PPI with mode 0 supported. Ports A, B, C High, and C Low
are buffered with 74ABT245 transceivers and pulled up to 5V.
COS Detection
Change of State Detection allows the card to generate an interrupt,
port by port. Either direction will set the change of state interrupt. Your
application can run much smoother by using this feature as processor
overhead is greatly reduced, polling is not required.
Counter/Timers
The optional 82C54 has three-sixteen bit counters within one chip. These
counters are useful for making frequency outputs, measuring frequency of
square waves, pulse width outputs, pulse width measurements etc.
The 104-DIO-48S is supported in most operating systems and include a free DOS, Linux and Windows 95/98/Me/NT/2000/XP/2003 compatible software package. This includes sample programs and source code in "C" and Pascal for DOS, and Visual Basic, Delphi, C++ Builder, and Visual C++ for Windows. Also included is a graphical setup program in Windows.
Downloads
Available Reference Manuals
- View / Download the 104-DIO-48S Manual (.PDF)
- View / Download the Software Reference Manual (.PDF)
Available Software Downloads
Available Datasheets
- View / Download the 104-DIO-48S Data Sheet (.PDF)
Further information about available ACCES Software:
- Redistributing Windows Drivers
- A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.
Specifications

Digital I/O
- Programmable Peripheral Int.: 82C55A
- Channels: 24 or 48, pulled up to 5V via 10K
- Buffered Channels: 24 or 48 bits (ports A, B, C-High and C-Low)
- Sink & Source Current: 64mA & 32mA
- Modes supported: Mode 0
- Change of State Detection: 48 Inputs (both 8255 groups, all 8 ports)
- Throughput: Up to 1 MByte/sec
- Power Output: Resettable fused +5V @ 500mA per 50 pin connector
Counter/Timer
- Peripheral Interface Timer: Type 82C54
- Counters: 3 x 16-Bit down counters
- Clock Frequency: 1 MHz Time Base, available to the user
- Software Support: Event Counter, Frequency Output, Frequency and Pulse Measurement
- Max Input Frequency: 10MHz
- Signal Type: TTL
General
- Power Required: +5V @50mA Typical
- Operating temperature: 0°C to +70°C, optionally -40°C to +85°C available
- Storage temperature: -50° to +120°C
- Interrupt Requests: Eleven channels, IRQ 3-7, 9-12, 14, 15
- Interrupt Status Registers: Two; One 8bit for COS, One single bit for C/T

CE testing & approval must be done at the system level, in the designed enclosure, and is not done on individual boards.
| Model | Price (USD) |
|---|---|
| 104-DIO-48S | 180.00 |
| 104-DIO-24S | 119.00 |