CALA
Call Subroutine at Location Specified by Accumulator
7-58
Syntax
CALA
Operands
None
Opcode
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
0
0
0
1
1
0
0
0
1
1
1
1
1
0
1
Execution
PC + 1
→
TOS
ACC(15:0)
→
PC
Status Bits
None
Description
The current program counter (PC) is incremented and pushed onto the top of
the stack (TOS). Then, the contents of the lower half of the accumulator are
loaded into the PC. Execution continues at this address.
The CALA instruction is used to perform computed subroutine calls.
Words
1
Cycles for a Single CALA Instruction
ROM
DARAM
SARAM
External
4
4
4
4+3p
Note:
When this instruction reaches the execute phase of the pipeline, two additional instruc-
tion words have entered the pipeline. When the PC discontinuity is taken, these two
instruction words are discarded.
Example
CALA
Before Instruction
After Instruction
PC
25h
PC
83h
ACC
83h
ACC
83h
TOS
100h
TOS
26h
Cycles