User guide

Interval Timer Tests

This test essentially emulates the realtime time provider and slave scheme found

in the Realtime Clock and Interval Device Driver functional speciﬁcation.

Note

A VMEbus P2 loopback connector is required. See Figure 4–1 for a

description of the loopback connections.

Using the -lp option enables the timers indeﬁnitely, making the module the

master time provider for test #4.

Timer 2 and timer 1 are programmed to mode 3, square wave mode. Timer 0

is programmed to mode 1. After the timers are initially programmed with the

appropriate mode and then loaded with a count value, the OUT output produces

a continuous, square wave output whose period is equal to the count value

multiplied by the period of the clock input. In this test timer 2 provides a major

clock which basically provides the start time of timer 0, and timer 1 produces

a much faster clock called the minor clock, which controls the rate that timer 0

counts down.

Timer 0 is the only interrupt that is enabled during this test. The event of OUT

transitioning from low to high should generate a CPU interrupt.

The ISR invoked due to the timer generated interrupt increments an interrupt

counter and sets a global ﬂag indicating the interrupt took place and that

software was dispatched to the correct point. The test veriﬁes that the interrupt

occurs, and that no more than one interrupt occurs per major clock cycle.

Console Command: i8254_diag -t 3

Command Options:

• -np: no print option; if speciﬁed no P2 connector message is printed

• -lp: prevents timers from being stopped at the end of the test; required before

invoking Test #4.

Timer 0 Loopback Test

This test exercises only timer 0. Timer 0 accepts its clock and gate input from the

P2 loopback connector. In this test, the Timer 0 inputs on the P2 connector can

be driven by a master Alpha VME board running test 3 with -lp speciﬁed on the

command line. See Figure 4–1.

This test essentially emulates the slave system found in the Realtime Clock and

Interval Device Driver functional speciﬁcation.

4–12 Diagnostics