Introduction.

Workshop PG5
Instructionlist
Conditional
jumps and calls:
Jumps and calls can contain a condition code. A condition code is a flag which
( depending on it's state ) executes a call or a jump. There are different condition
codes.:
1. You can activate a jump or a call depending on the state of the ACCU.
Example: If you use the condition code H, then the instruction will be
executed only if the ACCU is high ( equal 1 ). Condition code L executes
the instruction if the ACCU is low.
2. Another way to influence the behaviour of your program are the arithmetic
flags Negative, Positive, Zero, and Error. All the arithmetic instructions
and some of the communication instructions alter the state of the four flags.
The booklet with the instruction set summary, lists all the instructions and indicates
which of these instructions alter the ACCU or the arithmetic flags.
Examples:
We want to stop the acceleration of
the motor once the speed is, equal to
or higher than 200. Therefore we
compare the speed with 200. If the
value in the register called Motor
speed is equal or higher than 200,
then the Positive flag is set after the
CoMPare instruction.
The Jump Relative instruction checks
the Positive flag and jumps over the
program part which normally accelerates
the motor.
In this example we have a surveillance
flag which is used somewhere else in
the program. As soon as this flag is
set ( flag content equals 1 ) we want to
call the Program Block named Alarm.
The STart High instruction sets the
ACCU to 1 if the content of the surveillance
flag is 1. The Call Program
Block instruction on the next line
checks the ACCU and calls the Program
Block named Alarm as soon as
the ACCU is High.
MotorSpeed equ R
MinimumSpeed equ 200
COB 0
0
CMP
MotorSpeed
MinimumSpeed
JR P NoAcceleration
~
~
NoAcceleration:
~
~
ECOB
Surveillance equ F
Alarm equ PB
COB 0
0
STH Surveillance
CPB H Alarm
ECOB
PB Alarm
EPB
PG5-07-E © Saia-Burgess Controls Ltd. Page 7-13