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S3C84E5/C84E9/P84E9 INSTRUCTION SET
6-41
ENTER — Enter
ENTER
Operation: SP ← SP – 2
@SP ← IP
IP ← PC
PC ← @IP
IP ← IP + 2
This instruction is useful when implementing threaded-code languages. The contents of the
instruction pointer are pushed to the stack. The program counter (PC) value is then written to the
instruction pointer. The program memory word that is pointed to by the instruction pointer is loaded
into the PC, and the instruction pointer is incremented by two.
Flags: No flags are affected.
Format:
Bytes Cycles Opcode
(Hex)
opc 1 14 1F
Example: The diagram below shows an example of how to use an ENTER statement.
IP
Data
Address Data
40
41
42
43
Address Data
1F
01
10
Memory
Stack
0050
Before
0022
0040PC
22
IPH
IPL
Data
IP
Address Data
40
41
42
43
Address Data
1F
01
10
Memory
Stack
Enter
Address H
Address L
Address H
0043
0020
0110PC
Enter
Address H
Address L
Address H
Routine
110
20
21
22
After
00
50