Sharp MZ-80B Owner's Manual page 130

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:
Ds
Special
Turn
Power Halt
On Failure Process-
Test
Power
Alarm ing
ZSOA-CPU
D7-DO
I
AO-A IS
"'-.,
ADDRESS
DECODER
Temp.
Alarm
>
Turn
Heaters
On
Pressur-
Pressure
ize
System
Alarm
PORT A
BUS
A7
ZSOA-PIO
As
~---v
A5
v
A4
A3
v
A2
A,
v~
Ao
v
B"A C'D CE
I
t
FIGURE 7.0-3
CONTROL MODE APPLICATION
~SPE C.
TEST
TURN ON PWR
PWR. FAIL A L M
HALT
INDUSTRIAL
PRO CESS IN G
TEMP . ALM.
SYSTEM
HTR S.ON
PRESS.SYS
PRESS . ALM
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