User`s guide

E-Prime User’s Guide
Appendix A: Timing Test Results
Page A-13
Test Equipment Details
Timer Circuitry
The clock and counter circuitry of the BSOFT DIG-130 digital I/O card consists of three 16-bit
counters (C0, C1, C2) supported by a D71054C-10 (8254) IC driver with a 10.000MHz oscillator.
The 16-bit counters can be programmed for counting, generating square waves, or providing
precise interrupt timing functions. The default factory settings of the DIG130 configures the
counters to operate as independent 16-bit counters driven by the 10MHz oscillator. The default
configuration was modified (via the DIG130 P4 jumper block) to clock the first counter (C0) from
the 10MHz oscillator, and to clock the remaining to counters (C1 & C2) via external input signals.
The output of C0 was used as the external input signal to C1 and the output of C1 was used as
the external input signal to C2 resulting in a single cascaded 48-bit counter/timer with a frequency
of 10.000MHz. As configured, the 48-bit counter and clock provide a timer with a theoretical
maximum timing resolution of 1/10,000,000 second, or 100 nanoseconds, with a roll-over period
of approximately 325 days. The DIG130 card's timing accuracy was tested and verified using a
GoldStar model FC-2130 0-1.8 GHz Frequency Counter, and was determined to have an error
factor of 1.0000103, or 1.03 parts in 100,000. Secondary verification was performed with a
Tektronix TDS 620B Two Channel Digital Real-Time Oscilloscope (500MHz, 2.5 GS/s). The
down counters of the DIG130 cards are controlled via TTL lines between the TS and the ES.
Digital I/O
Digital I/O on the DIG130 was supported by a D71055C-10 (82C55) IC configured as three 8-bit
ports. The individual ports can be configured as either input or output. Upon software
initialization, the TS configures Port A & Port B as input and Port C as output. The ES configures
Port A & Port B as output and Port C as input. The current version of the custom timing software,
which runs on the TS, supports a number of different test types/methods (described below). In
each test, the software waits for an acknowledge signal from the ES, collects the test data,
caches the results locally, and then writes the data to disk at the end of the test. The DIG130 in
the TS was configured as base address 200 Hex, and interrupts from the card were disabled.
Peripherals
The TS station relies on a number of peripheral components to conduct its work. The following is
a description of each device:
PST, Serial Response Box Model 200a –The PST Serial Response Box (SRBOX) was used
only as an interface device to provide support circuitry for the PST Refresh Detector (i.e., it was
NOT directly connected to the TS via a serial cable as would be the case if the device was being
used as an input device). The Refresh Detector circuitry on the SRBOX is active and available
for use as long as the device is powered on.
PST, Refresh Detector – The PST Refresh Detector (RD) was attached to the monitor of the ES
machine and used to detect when a stimulus appeared on screen. The oscilloscope leads from
the device were wired directly into the input lines of the DIG130 card installed in the TS.
Qtronix, Keyboard Model QX-032H (modified for use) – the Qtronix keyboard was modified on
switch 5 to parallel in a high-speed reed relay (Radio Shack # 275-232, 5VDC Reed Relay rated
at 125V, 1A). The relay was triggered via an external 5V TTL input to a 7406 open collector hex
inverter. An external o-scope probe lead was wired to the opposite side of the switch so that the
TS could verify and timestamp when the keyboard device was activated (i.e., when the switch
was actually closed). The delay in reed switch activation was observed to be 0.02ms +/- 0.01ms.
The test was performed using both the DIG130 timer card and the Tektronix Oscilloscope.