XC2200 Derivatives
System Units (Vol. 1 of 2)
Central Processing Unit (CPU)
User’s Manual
4-38
V2.1, 2008-08
CPUSV2_X, V2.2
For processing an accepted interrupt or a TRAP, register CSP is automatically loaded
with the segment of the vector table (defined in register VECSEG).
Note: For the correct execution of interrupt tasks in non-segmented memory mode, the
contents of VECSEG must select the same segment as the current value of CSP,
i.e. the vector table must be located in the segment pointed to by the CSP.
Note: After a reset, register CSP is automatically loaded from register VECSEG.
The Instruction Pointer IP
determines the 16-bit intra-segment address of the currently
fetched instruction within the code segment selected by the CSP register. Register IP is
not mapped into the XC2200’s address space; thus, it is not directly accessible by the
programmer. However, the IP can be modified indirectly via the stack by means of a
return instruction. IP is implicitly updated by the CPU for branch instructions and after
instruction fetch operations.
CSP
Code Segment Pointer
SFR (FE08
H
/04
H
)
Reset Value: xxxx
H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
SEGNR
-
-
-
-
-
-
-
-
rh
Field
Bits
Type
Description
SEGNR
[7:0]
rh
Specifies the code segment from which the current
instruction is to be fetched.
IP
Instruction Pointer
- - - (- - - -/- -)
Reset Value: 0000
H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ip
0
(r)(w)h
r
Field
Bits
Type
Description
ip
[15:1]
h
Specifies the intra segment offset from which the
current instruction is to be fetched. IP refers to the
current segment <SEGNR>.