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INSTRUCTION SET
JTF
address
Jump
If
Timer
Flag
Is
Set
I 0 0 0 1 I 0 1 1 0 I I
a7
a6
as
a4
I
a3
a2
a1
ao
I
This is a 2-cycle instruction.
Control
passes
to
the
specified address
if
the
timer
flag is set to one,
that
is,
the
timer/counter
register has overflowed.
Testing the
timer
flag resets it
to
zero. (This
overflow initiates
an
interrupt
service sequence
if
the timer-overflow
interrupt
is
enabled.)
(PC
O
-
7
)--
addr
(PC) = (PC)+2
Example: JTF1: JTF TIMER
If
TF=1
If
TF=O
;JUMP
TO 'TIMER' ROUTINE
;IFTF=1
JTO
address
Jump
If
Test
0
Is
High (Not in 8021)
I 0 0 1 1 I 0 1 1 0 I I
a7
a6
as
a4
I
a3 a2
a1
ao
I
This is a 2-cycle instruction. Control passes to the
specified address
if
the test 0 signal
is
high (=1).
(PCO-7)--
addr
(PC) = (PC)+2
If
TO=1
If
TO=O
Example: JTOHI:
JTO
53
;JUMP TO LOCATION
53
DEC
;IF
TO=1
JT1
address
Jump If Test 1
Is
High
I 0 1 0 1 I 0 1 1 0 I I
a7
a6
as
a4
I
a3 a2
a1
ao
I
This
is
a 2-cycle instruction.
Control
passes to the
specified address
if
the test 1 signal
is
high (=1).
(PCO-7)--
addr
If
T1=1
(PC) = (PC)+2 If
T1=O
Example: JT1HI: JT1
COUNT
;JUMP
TO
'COUNT' ROUTINE
;IF
T1=1
JZ
address
Jump
If
Accumulator
Is
Zero
This
is
a 2-cycle instruction. Control passes
to
the
specified address
if
the
accumulator
contains all
zeros at the time this
instruction
is
executed.
(PCO-7)
--
addr
(PC) =
(PC)+2
Example: JACCO:
JZ
OA3H
Mnemonics
copyright
Intel
Corporation
1976.
4·21
If
A=O
If
At-O
;JUMP TO LOCATION 'A3' HEX
;IF
ACC
VALUE IS ZERO