Freescale Semiconductor StarCore SC140 - Manual (Page 536)

A-222 SC140 DSP Core Reference Manual
LPMARKx
LPMARKB
For long loops (SLF=0), this prefix bit is placed at LA-2 (two sets before the last set of the loop). It
instructs the active loop to decrement LCn and issue a jump delayed operation (with 2 delay slots) to SAn,
if LCn is greater than one. If LCn is less than or equal to one, then the LCn register and the LFn bit are
cleared. For short loops (SLF=1) of two execution sets, this prefix bit is placed at the first set of the loop
(SA).
LPMARKA
For long loops (SLF=0), this prefix bit is placed at LA (the last set of the loop) and is used in special cases.
It instructs the active loop machine to decrement LCn and jump to SAn if LCn is greater than one. If LCn
is less than or equal to one, then the LCn register and the LFn bit are cleared. This prefix bit is used only in
cases where there is a possibility that the loop machine might not be able to identify LPMARKB, which is
normally used in long loops. An example is the case of nested loops where the inner loop may be skipped
with SKIPLS directly to the LA of the enveloping loop. In case of short loops (SLF=1) of one execution
set, LPMARKA is always placed at the first set of the loop (SA).
Status and Conditions that Affect LPMARK Execution
The loop flag (LFn), short loop flag (SLFn), and loop counters (LCn) affect the response as described in
the description above.
Table A-17. Combinations of LPMARKx Use
LPMARKA LPMARKB LFn SLF LCn Description
no LPMARKB set clear
> 1
LCn decrements by one and a jump with two delay slots
to SAn occurs. LPMARKs appearing in the delay slots
are ignored.
≤ 1
LCn and LFn are cleared. The active loop is terminated.
Every LPMARKA that appears in the next two delay slots
is ignored.
LPMARKA no set clear
> 1
LCn decrements by one and a jump to SAn occurs.
≤ 1
LCn, LFn, and SLF are cleared. The active loop is termi-
nated.
no LPMARKB set set
> 1
LCn decrements by one and LPMARKs appearing in the
next execution set are ignored. A jump with one delay
slot to SAn occurs.
≤ 1
LCn, LFn, and SLF are cleared. The active loop is termi-
nated. LPMARKs appearing in the next execution set are
treated.
LPMARKA no set set
> 1
LCn decrements by one and a jump to SAn occurs.
≤ 1
LCn, LFn, and SLF are cleared. The active loop is termi-
nated.
LPMARKA LPMARKB set clear
> 1
If LPMARKA and LPMARKB appear together,
LPMARKA belongs to the inner loop and LPMARKB
belongs to the outer loop.
If the inner LCn
> 1, the LPMARKB is ignored and the
LPMARKA is executed.
If the inner LCn
≤ 1, the inner LCn and the inner LFn are
cleared. The active inner loop is terminated and the
LPMARKB is executed.
LPMARKA LPMARKB set set
> 1