Sharp MZ-80B Owner's Manual page 132

123
7.3 CONTROL INTERFACE
A typical control mode application is illustrated in Figure 7.0-3. Suppose an industrial process is to be monitored.
The occurrence of any abnormal operating condition is to be reported to a Z-80A-CPU based control system. The
process control and status word has the following format:
Special
Tum Power Halt
On
Failure Process-
Test
Power Alarm
ing
ZBOA-CPU
.......
07-DO
I
AO-A 15
....,
ADDRESS
DECODER
Temp .
Alarm
:>
Turn
Heaters
On
Pressur-
Pressure
ize
System
Alarm
PORT A
BUS
A7
ZBOA-PIO
A6
~
As
v
A4
A3
v~
A2
AI
1/'1
SPEC. TEST
TURN ON PWR
PWR. FAIL ALM
HALT
TEMP. ALM .
HTRS.ON
PRESS.SYS
Ao
~
PRESS.ALM
B'A
C'D CE
t
t
FIGURE 7.0-3
CONTROL MODE APPLICATION
INDUSTRIAL
PROCESSING
SYSTEM
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.
X X
Whenever Mode 3 is
selected, the next control word sent to the port must be an 1/0 select word. In this example we
wish to select port data lines AS, A3 and AO as inputs and so the following control word is written:
Do
0 0 0 0 0
Next the desired interrupt vector must be loaded (refer to the CPU manual for details);
0