rtd DM5816, User Manual

Page: 12 / 44

DM5816/DM6816 RTD Embedded Technologies, Inc.
12
NOTE: When using multiple modules sharing the same interrupt, only one module should
have the G jumper installed. The rest should be disconnected. Whenever you operate a
single module, the G jumper should be installed. Whenever you operate the module with
interrupt sharing disabled, the G jumper should be removed.
Fig. 1-2 – Interrupt Channel Select Jumpers, P4 and P16
Fig. 1-3 – Pulling Down the Interrupt Request Line
P5 — 8254 Clock and Gate Source Select
(Factory Settings: See Figure 1-4)
This header connector, shown in Figure 1-4, lets you select the clock sources for the three 8254 16-bit
timer/ counters. Figure 1-5 shows a block diagram of the timer/counter circuitry to help you in making
these connections.
The clock source for Counter 0 is selected by placing a jumper on one of the two leftmost pairs of pins on
the header, OSC or EC0. OSC is the on-board 8 MHz clock, and EC0 is an external clock source which
can be connected through I/O connector P6, pin 1. Counter 1 has three clock sources: OT0, which
cascades it to Counter 0; OSC, which is the on-board 8 MHz clock; and EC1, which is an external clock
source connected through I/O connector P6, pin 5. Counter 2 has three clock sources: OT1, which