Mode Selection: The operational modes of the board
are selected by setting the following control bits during
a write cycle to the Control and Status Register (CSR).
The CSR may be read at any time to verify the current
operating mode. The function of each bit in the CSR is
defined as follows.
D08 — Enables DAC outputs to the P3
connector
D09 — Initiates digital-to-analog
conversion
D10 — Not used
D11 to D13 — Test mode control bits
D14 — Operates Fail LED
D15 — Not used
Test Mode: The DAC board may be used in
conjunction with other VMIC boards and VMIC’s
AMXbus backplane for extensive fault detection and
isolation. There are two dedicated analog signal lines
that are used by the DAC board. Loopback tests may be
executed primarily for testing the Analog-to-Digital
Converter (ADC) board by utilizing any one of the
eight DAC outputs.
While in a test mode, the eight DAC outputs may be
isolated from the P3 output connector so that
user-connected devices are not affected by testing.
Also, the testing may be performed in conjunction with
real-time control of the user-connected devices,
providing real-time fault detection capabilities.
Analog Input Test Mode: Any one of the eight
analog outputs may be multiplexed to an analog test bus
(Test Bus 1). This analog bus is used to verify the
operation of the analog input multiplexer expansion
board that supports Built-in-Test. VMIC’s AMXbus
supports the analog Built-in-Test concepts.
Analog Output Testing: Any one of the eight analog
outputs may be switched to the analog output test bus
(Test Bus 2). This bus is routed over the P2 AMXbus
analog backplane to a VMIC ADC which verifies the
analog output of each of the eight DACs on the
VMIVME-4116 board.
System Reset: Application of the system reset signal
via the VMEbus initializes the board into a state with all
analog outputs disconnected from the P3 connector if
either the JFET switch or output isolation relay options
are installed. If no output isolation switches or relays
are installed (see the Ordering Options), then system
reset initializes all analog outputs to the P3 connector to
0.0 V. The analog test bus outputs are disconnected from
the P2 connector upon system reset.
Front Panel Fail LED: If an error condition is
detected during the diagnostics, a front panel Fail LED
may be illuminated under software control for a visual
failure indication. The LED is illuminated upon power
up clear (system reset) and is extinguished upon
successful diagnostic execution.
Analog Output Channels: Eight analog output
channels
The analog output equation for offset binary bipolar
operation:
(-10 V to +10 V) is VOUT = -10 V + [(Digital Code 10 x 20)]
65536
ELECTRICAL CHARACTERISTICS
Data Transfer: A16/D8, D16
Analog Output (Voltage output at RLOAD =
2 kΩ):
Bipolar: -10 to +10 V at 5 mA
Output Impedance:
Standard model — 0.15 Ω
Optional output isolation switches (JFET switch)
—100 Ω
Optional output isolation relays — 0.2 Ω
D/A Input Code:
Bipolar: Offset binary, two’s complement binary
Resolution: 16 bits
Accuracy (Typical at 25 °C)*
Gain Error: Adjusted to ±1/2 LSB
Offset:
Bipolar: Adjusted to ±1/2 LSB
Differential Linearity Error: ±0.003 percent of
FSR (Full-Scale Range)
Linearity Error: ±0.0015 percent of FSR
Drift (Typical Unless Otherwise Stated):
Gain Drift: ±10 PPM/°C
Zero Drift: ±5 PPM of FSR/°C
VMIVME-4116
