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Manual MPAD128.D1g
Mode 0
is the most frequently used mode of operation wherein:
a. There are two 8-bit ports (A and B) and two unavailable 4-bit ports (C Hi and
Lo).
b. Any port can be configured as an input or an output.
c. Outputs are latched.
d. Inputs are not latched.
Mode 1 is used for strobed input/output. In this mode Port A and Port B use the lines
of Port C to generate and accept control signals associated with data transfer. See the
8255-5 PPI specification for control line assignments.
Mode 2 is used for bi-directional 8-bit bus applications. See the 8255-5 specification.
Bit D4, A, sets input or output for port A (DIO 0-7). 1=input, 0=output.
Bit D1, B, sets input or output for port B (DIO 8-15). 1=input, 0=output.
Analog Inputs
Programming the Analog Inputs is a straightforward task, consisting of a few consistent
steps. Refer to the register definitions in the sections above when reading these
instructions.
The first step every time you use the card is to initialize it. This five step process is as
follows:
Reset the Card and Point List Index: Base + 10 bit 1
Calibrate the Card: Base + 10 bit 3
Setup the Points: Base addresses 0 through E, even.
Configure the A/D Control Register: Base + 10
Reset the Card and Point List Index: Base + 10 bit 1
"Setup the Points" is up to 8 writes, to addresses 0, 2, 4, etc, with the last write setting
the Loop bit as well as the channel information. Additionally, each point can have the
Timer or Pause bit set to determine various timing characteristics. It is important that
writing to the point list not be performed while the A/D chip is working. Make sure you
issue a Stop (Base+10 bit 0) or a Reset (Base+10 bit 1) before loading the point list.
Also, when done loading points in the list, you must issue a Reset (Base+10 bit 1).
Once the card is initialized, data acquisition can begin. This is accomplishable in a
variety of methods, two of which we will discuss here. For more information on
acquisition methods, consult the LM12H458 chip specification.