Technical Description; Introduction; Description - ZiLOG Z80-AIO Hardware User Manual

SECTION 6:
6.1
The following section contains a detailed description of the
Operation and logical throughput of the AIO.
directed to use the accompanying schematic at the end of the
is not noticeably discriminated in the description.
references to analog input are applicable to both boards.
The boards
6.2

Description

The AIO is programmed äs I/O ports.
address bus lines AB3-AB7 to select the board itself.
decodes address bus lines ABO, ABI, and AB2.
Conversion of an input channel is started by writing the
channel number to the board (location 88H).
lines AB2, ABI, and ABO are logic 0 and WR- is active, Pin l
of IC22 will go high latching the input channel number into
IC23. The same signal also triggers the first one-shot in
ICH. This one-shot times out 20 microseconds to allow for
settling of the input multiplexers, instrumentation
amplifier, and sample-hold amplifier.
time, it turns the sample-hold amplifier to Hold by
outputting a pulse from Pin 13, ICH, to Pin 8 of IC12.
same pulse also triggers the second one-shot in ICH at Pin
9. The Output of the second one-shot, Pin 5 of ICH, is
connected to Pin 18 of SMS which immediately Starts
conversion in the A/D Converter. The Output of the first
one-shot, Pin 13, of ICH, and Pin 22 of SM3 go through an
the data bus (DO) at Pin 13 of IC27 to provide Status
DO is low during the conversion process. DO is
high when conversion is complete and data is ready at the
Output of the A/D Converter.
Converter, SM3, on Pins 1-6 and 27-32.
connected through IC33 and IC34 to the PIO, IC32, Pins 7-15
and 27-30. When the AIO is read, address lines AB2 and ABI
are egual to logic 0.
data are Output when ABO is logic 0 and the four most
significant bits are Output when ABO is logic 1.
connected to the PIO from IC27, Pin 3, to IC32, Pin 6.
The AIB, being a subset of the AIO,
The Output of the "OR" gate connects to
Data is Output from the A/D
The eight least significant bits of
27
The reader is
All
IC20 and IC26 decode
Jumpers JP29
At the end of this
The Outputs are then
ABO is
IC21
This