Status Register Fields - Texas Instruments TMS320C2x User Manual

6.2.1

Status Register Fields

Table 6−2. Status Register Fields
6.2.2 Stack Pointer, Frame Pointer, and Local Variable Pointer
Table 6−2 shows all of the status fields used by the compiler. Presumed value
is the value the compiler expects in that field upon entry to, or return from, a
function. A dash in this column indicates that the compiler does not expect a
particular value. The modified column indicates if code generated by the
compiler ever modifies this field.
(a) TMS320C2x, TMS320C2xx and TMS320C5x fields
Field Name
ARP Auxiliary-register pointer
C Carry
DP Data page
OV Overflow
OVM Overflow mode
PM Product shift mode
SXM Sign-extension mode
TC Test-control bit
(b) TMS320C5x-only fields
Field Name
BRAF Block-repeat active flag
NDX Index-register enable bit
TRM Enable multiple TREGs
The compiler creates and uses its own software stack for saving the function
return addresses, allocating local (automatic) variables, and passing argu-
ments to functions. The internal hardware stack is not used to save the function
return address except in cases where the compiler can be certain the call
depth (the number of function invocations on the stack at the same time) does
not exceed eight levels. When a function requires local storage, it creates its
own working space (local frame) from the stack. The local frame is allocated
during the function's entry sequence and deallocated during the return
sequence.
Three registers, the stack pointer (SP), the frame pointer (FP), and the local
variable pointer (LVP), manage the stack and the local frame.
Register Conventions
Presumed Value
1
−
−
−
0
0
−
−
Presumed Value
−
0
0
Run-Time Environment
Modified
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Modified
Yes
No
No
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