A.1.4 encoding notation, A.1.3 – Freescale Semiconductor StarCore SC140 User Manual
Page 320
A-6
SC140 DSP Core Reference Manual
DSP Core Instruction Set
A.1.3 Data Representation in Memory for the Examples
For the examples in this appendix, the convention for the representation of data in memory is to show the
same order in memory as is in the source register for a write. For example, a 32-bit write from a register
containing $12345678 to address $100 will be shown as: ($100) = $12345678. The exact order of
multi-byte operands in memory depends on the endian mode, and is described in
A.1.4 Encoding Notation
The instruction encoding is defined for each instruction under Instruction Formats and Opcodes and
Instruction Fields. Each instruction field may not be contiguous in the opcode, but the order of the bits in
each field is consistent from the opcode to the definition of the field. For example, in the MOVE.B
instruction, the encoding for the opcode is
The order of bits for a16 (AAA---A) is the MSB in the first bit at the left-most position in word 1. The LSB
is the right-most position in word 2. If written out fully, the encoding would be:
A more complicated example is for BSR, where two fields are intermixed. The order for each field is
maintained, monotonically decreasing from left to right.
The definition for the field is
:
If the field was written out in the encoding table, it would appear as follows:
15
8
7
0
MOVE.B (a16),DR
0
0
0
1
H H H H A
A
A
0
1
1
1
0
1
0
0
A
A
A
A
A
A
A
A
A
A
A
A
A
15
8
7
0
MOVE.B (a16),DR
0
0
0
1
H
H
H
H
A15 A14 A13
0
1
1
1
0
1
0
0
A12 A11 A10 A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
BSR
>label
0
0
1
0
a
0
1
1
A
A
A
1
1
a
a
a
1
0
0
A
A
A
A
A
A
A
A
A
A
A
A
a
displacement
(>label)
aaaaaAAAAAAAAAAAAAAA0
20-bit signed PC relative displacement
BSR
>label
0
0
1
0
a20
0
1
1
A15 A14 A13
1
1
a19 a18 a17
1
0
0
A12 A11 A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
a16