Functions of the board
PA 200
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9
FUNCTIONS OF THE BOARD
9.1
Introduction
The
PA 200
requires no initialization. It can be used immediately after power has
been turned on and after successful reset of the CPU. The address decoding relates
to the 64 KB I/O address area. Both lower address bits are decoded for selecting 4
blocks of 8 outputs. The higher address bits are compared with the on-board
adjusted switches ; the board is enabled when they are identical. The control logic
takes over coordination between the board and the microcomputer.
The peripheral signals are connected over the front connector and transmitted to
the optically decoupled power transistors.
9.2
Programming
For information exchange between the CPU and the board 4 addresses are
assigned, which are differentiated through the 2 lowest address bits. The highest
address bits A2 - A15 are compared with the DIP switch as described in chapter 7.
The board needs no software initialization. It can be directly selected over its
adjusted address with the basic command OUT, for example.
Suppose the address is 0390 hexadecimal.
The 32 digital outputs can be operated directly with the commands :
-
OUT &H0390, data
-
OUT &H0391, data
-
OUT &H0392, data
-
OUT &H0393, data.
Output 1 corresponds to bit 0 of OUT &H0390. Output 32 corresponds to bit 7 of
OUT &H0393.
I.e. : Set outputs 1 and 10 on logical "1"
-
OUT (&H0390),&H01
-
OUT (&H0391),&H02
The output data remain so long at the respective outputs until they are overwritten
by a new output. This occurs also after power ON reset.
