Program Control
Program Control
The program control logic and program address generation logic work together to provide proper
program flow. Normally, the flow of a program is sequential: the CPU executes instructions at
consecutive program memory addresses. At times, a discontinuity is required; that is, a program
must branch to a nonsequential address and then execute instructions sequentially at that new
location. For this purpose, the C28x supports interrupts, branches, calls, returns, and repeats.
Proper program flow also requires smooth flow at the instruction level. To meet this need, the
C28x has a protected pipeline and an instruction-fetch mechanism that attempts to keep the
pipeline full.
Branches
Branch Types and Range
Branch
offset +/-32K
2-word
instruction
Long
Branch
absolute 4M
2-word
instruction
PC
Short Branch
offset +127/-
128
1-word
instruction
Program
Memory
0x000000
0x3FFFFF
3 Branch Types
The PC can access the entire 4M words (8M bytes) range. Some branching operations offer 8-
and 16-bit relative jumps, while long branches, calls, and returns provide a full 22-bit absolute
address. Dynamic branching allows a run-time calculated destination. The C28x provides the fa-
miliar arithmetic results status bits (Zero, oVerflow, Negative, Carry) plus a Test Control bit
which holds the result of a binary test. The states of these bits in various combinations allow a
range of signed, unsigned, and binary branching conditions offered.
C28x - Appendix C - Assembly Programming C - 3
To Next Page
Loading...
Need help?
General
