DM6210 datasheet(32/91 Pages) ETC

32 / 91 page

3-4

Timer/Counters

An 8254 programmable interval timer provides three 16-bit, 8 MHz timer/counters to support a wide

range of timing and counting functions. These timer/counters can be cascaded or used individually for many

applications.

Each timer/counter has two inputs, CLK in and GATE in, and one output, timer/counter OUT. The clock

sources for the timer/counters can be selected using jumpers on header connector JP1 (see Chapter 1). The

timer/counters can be programmed as binary or BCD down counters by writing the appropriate data to the

command word, as described in Chapter 4. The command word also lets you set up the mode of operation. The

six programmable modes are:

Mode 0

Event Counter (Interrupt on Terminal Count)

Mode 1

Hardware-Retriggerable One-Shot

Mode 2

Rate Generator

Mode 3

Square Wave Mode

Mode 4

Software-Triggered Strobe

Mode 5

Hardware Triggered Strobe (Retriggerable)

These modes are detailed in the 8254 Data Sheet, reprinted from Intel in Appendix C.

Digital I/O

The DM6210 has 16 TTL/CMOS-compatible digital I/O lines which can be directly interfaced with

external devices or signals to sense switch closures, trigger digital events, or activate solid-state relays. The

lines can be programmed as inputs or outputs in groups of 4 bits. There is also a special latched input mode

which allows the digital inputs to be latched on an external clock edge for time critical applications. Solder

pads for activating pull-up or pull-down resistors are included on the module.

Interrupts

The DM6210 has 7 software-selectable interrupt sources: end-of-convert, 8254 timer/counter output 0,

8254 timer/counter output 1, 8254 timer/counter output 2, external clock for timer/counter 2 brought onto the

module through CN3, Port 0 latch status and Port 1 latch status. The end-of-convert signal can be used to

interrupt the computer when an A/D conversion is completed. The 8254 timer/counter outputs can be used to

generate an end-of-count interrupt. The external clock 2 interrupt can be used to generate interrupts at any

desired interval from an external source. The Port 0 and Port 1 latch status bits can be used to generate an

interrupt when digital data has been strobed into the digital input latch.

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