Zilog Z08470 - Manual (Page 222)

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UM008101-0601 Parallel Input/Output
Control Interface
A typical control mode application is illustrated in Figure 16. In this
example, an industrial process is to be monitored. The occurrence of any
abnormal operating condition is to be reported to a Z80 CPU-based control
system. The process control and status word has the following format:
The PIO may be used as follows. First, Port A is set for Mode 3 operation
by writing the following control word to Port A.
Whenever Mode 3 is selected, the next control word sent to the port must
be an I/O select word. In this example, port data lines A5, A3, and A0 are
selected as inputs, and the following control word is written:
Next, the appropriate interrupt vector must be loaded (refer to the Z80 CPU
User’s Manual for details):
An interrupt control word is next sent to the port:
The mask word following the interrupt mode word is:
D7 D6 D5 D4 D3 D0
Halt
Processing
D2 D1
Special
Test
Turn On
Power
Power
Failure Alarm
Temp.
Alarm
Turn On
Heaters
Pressurize
System
Pressure
Alarm
1 1 X X
D7 D6 D5 D4 D3 D0 D2 D1
1 1 1 1
0 0 1 0
D7 D6 D5 D4 D3 D0 D2 D1
1 0 0 1
V5 V4
D7 D6 D5 D4 D3 D0 D2 D1
V3 V2 V1 0 V1 V6
Interrupt Control
1 1
D7 D6 D5 D4 D3 D0 D2 D1
0 1 1 1 1 0
Enable
Interrupts
OR
Logic
Active
High
Mask
Follows