Chapter 4: Programming the AD12-8
Manual Number: 00650-014-4
Page 4-3
A/D Registers
A/D data are in true binary form and are latched in the A/D registers at the end of each conversion.
These are read at BASE ADDRESS and BASE A1 in low-byte/high-byte sequence.
The data are available until the end of the next A/D conversion. The status of digital output bits
OP0-OP3 are contained in the low byte register.
Base + 0 Read
: Contains the lower four bits of the A/D converter output in binary form and the
status of digital output bits OP0-OP3 in binary form.
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AD0-AD3:
The lower four bits of the A/D conversion, AD0 is the least-significant bit.
OP0-OP3:
The status of digital outputs OP0-OP3.
Base + 1 Read:
Contains the upper eight bits of the A/D converter output in binary form.
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AD4-AD11:
The most significant eight bits of the A/D conversion, AD11 is the most-
significant bit.
Base + 1 Write:
A write to this location starts an A/D conversion. The data written is irrelevant.
This causes the EOC bit of the status register to go high until the conversion is complete.
Digital I/O
The AD12-8 card provides 16 bits of digital I/O capability. If the card is to be used with an AT16-
P input multiplexer expansion card, then half of these bits are used for gain programming and
multplexer channel selection. If the AT16-P is not to be used, then these bits may be programmed
using the control registers as described earlier in this section.
The AD12-8 card provides eight individually programmable digital inputs/outputs. Eight jumpers
determine the input/output configuration of the eight digital lines identified as DIO0-DIO7. If no
jumpers are installed, all eight lines are configured as inputs. Installation of a jumper at locations
DO-D7 convert the corresponding line to an output.
Digital inputs are read from a register at BASE A 3. Digital outputs are written to a
register at BASE A 0.
