Analog Devices ADSP-BF535 Blackfin, Hardware Reference Manual

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ADSP-BF535 Blackfin Processor Hardware Reference 4-13
Program Sequencer
These five ways of accessing the
CC
bit are used to control program flow.
The branch is explicitly separated from the instruction that sets the arith-
metic flags. A single bit resides in the instruction encoding that specifies
the interpretation for the value of
CC
. The interpretation is branch on true
or false.
The comparison operations have the form
CC = expr
where expr involves a
pair of registers of the same type (for example, Data registers or Pointer
registers, or a single register and a small immediate constant). The small
immediate constant is a 3-bit (–4 through 3) signed number for signed
comparisons and a 3-bit (0 through 7) unsigned number for unsigned
comparisons.
The sense of
CC
is determined by equal (
==
), less than (
<
), and less than or
equal to (
<=
). There are also bit test operations that test whether a bit in a
32-bit register is set.
Conditional Branches
The Sequencer supports conditional branches. These are
JUMP
instructions
whose execution is based on testing an
IF
condition that is based on the
status of the
CC
bit. The target of the branch is a PC-relative address from
the location of the instruction plus an offset. The PC-relative offset is an
11-bit immediate value that must be a multiple of two (bit zero must be a
zero). This gives an effective dynamic range of –1024 to +1022 bytes.
For example, the following instruction tests the
CC
flag and, if it is posi-
tive, jumps to a location identified by the label
dest_address
.
IF CC JUMP dest_address ;
Conditional Register Move
For condition handling where the value of a register is set based on the
condition code, a conditional move instruction can be used instead of a
branch statement. A register move can be performed, depending on