Chapter 4 Hardware Overview
PCI/PXI-6703/6704 User Manual 4-2 www.natinst.com
Bus Interface Circuitry
The bus interface circuitry monitors the PCI or PXI bus. If the bus address
matches the 6703/6704 device’s address, the board is enabled and the
corresponding register on the 6703/6704 is accessed.
I/O Connector
All user I/O is transmitted through a 68-pin connector. Refer to the Custom
Cabling section in Chapter 1, Introduction, and to Chapter 3, Signal
Connections, for additional information.
Nonvolatile RAM/DAC Control
The 6703/6704 devices have one 16-bit DAC that is time-division
multiplexed to create all the output channels. Each channel has a
track-and-hold circuit to maintain the channel value between DAC updates.
On the 6703, the DAC is multiplexed to create 16 voltage outputs and two
calibration channels. On the 6704, the DAC is multiplexed to create
16 voltage outputs, 16 current outputs, and four calibration channels.
Data is stored in a nonvolatile RAM (nvRAM). The nvRAM/DAC control
reads the DAC channel data stored in the nvRAM and updates the DAC
periodically. The nvRAM/DAC control also controls the analog
demultiplexing circuits to route the DAC output to the correct analog output
channel. You can choose to save nvRAM data so that the current output
values will become the power-on states.
Digital I/O Control
The 6703/6704 devices have eight digital I/O lines configured as one 8-bit
port. You can configure each line independently as an input or output. The
DIO lines have 16 mA of sink capability and 16 mA of source capability.
All digital lines are TTL compatible. At power up, all digital lines are
configured as inputs.
Temperature Sensor
The onboard temperature sensor measures the air temperature flowing over
the board. This sensor is positioned near the onboard precision voltage
reference, which can be affected by extreme temperatures. This sensor has
a serial digital interface.
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