Example Of Control With Machine Language - Sharp MZ-80P4 Instruction Manual

Example of control with machine language'
The example of program for controlling this printer with machine language is shown below. The
method of control varies, depending on the ROM unit used. The example shown below represents
reference subroutine program which constitutes the most basic part of the control.
• Control as printer for MZ-80B/MZ-80A
[Concept of printer control
I
Start
. - - - - - - + 1
Checks BUSY signal
Yes
Is the printer
ON LINE?
Transmits control
code or printing
data code to the
printer.
Is
there
transfer
data?
No
[Printing data transfer routine
I
No
No
29
Start
BUSY signal input
Low level?
Transfers data
code
Makes DATA STH
signal high.
BUSY signal input
High level?
Makes DATA STB
signal low.
Return
IN A. (FEH)
~
Ace. - Data code
/ OUT (FEH), A
S
Ace.
+-
SOH
/ OUT (FEll), A
IN A, (FE H)
[
When the printer]
receives data
code, BUSY
signal becomes
high.
S
Ace.
+-
oon
lOUT (FEH), A