With the advent of the LS7166 24 Bit Multi-mode Counter chip by LSI Computer Systems, Inc., it became possible to design a highly versatile yet inexpensive counter interface board for the IBM-PC computer. The MC-4A Multi-Mode Counter Board plugs into an 8 bit expansion slot of an IBM-PCXT, 286 or higher, giving the user the ability to count DC to 8 MHz signals in either up/down, binary, binary coded decimal, 24 hour clock, divide-by-N, X1 or X2 or X4 quadrature and single cycle modes. Because the MC-4A has user selectable jumpers, it is extremely flexible in its ability to change I/O address, digital filter setup, interrupt selection and chip configuration.

FEATURES & APPLICATIONS:

Programmable Count Modes: Up/Down, Binary, BCD, 24 Hour Clock, Divide-by-N

Count Cycles: 24 bit wraparound or single cycle

Quadrature Count Modes: X1, X2, X4

Digital Filter: Upper limit cut-off filter and user adjustable 92 Hz to 8.0 MHz with 20 MHz in quadrature X4.

Comparator Outputs: Carry, borrow or equal (also Interrupts)

Flexible Addressing: User selectable from 200 to 3F8 (hex)

Low cost and high reliability

Factory Direct Support

Rugged Interface Plug: No Ribbon Cable Connectors

Interface Easily to Optical Encoders

CIRCUIT DESCRIPTION:

The circuit will accept a 0 to +5 volt signal from TTL or CMOS sources at the interface connector. The signal is filtered by an R-C network and clamped at ground and +5 volts by an input protection diode circuit. The signal is then processed by a digital filter circuit to reject noise above a critical frequency. This upper frequency limit is user configurable. The signal is then counted in the LS7166 24 bit multi-mode counter I.C. An index signal can be input at the interface connector to function as a hardware reset or load signal to the counter. Four counter circuits are provided on this board to allow counting four channels simultaneously. The counters are interfaced to the IBM PC bus via address decoding and data interface circuitry. Borrow and/or carry outputs can be connected to an IBM-PC interrupt line to trigger interrupt service routines. Also, these Borrow and Carry outputs are also connected to the interface connector plug. A 1 amp fused +5 volt power source from the computer bus is provided at the interface connectors to power external devices such as optical encoders. Also a +12 volt power source, fused at 1 amp, is provided to power for other circuits. Both of these power sources are from the computer's power supply.

SPECIFICATIONS:

The MC-4A Multi-Mode Counter Board is supplied with a comprehensive set of demonstration programs to assist the user in understanding the many functions of the LS7166 Counter Chip. These programs are supplied on a DOS compatible floppy disk and contain both the .EXE executable program as well as the complete source code.