Cryptographic Acceleration Unit (CAU)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
5-4
Freescale Semiconductor
5.2.3
CAU General Purpose Registers (CAn)
The six CAU general purpose registers are used in the CAU commands for storage of results and as
operands for the various cryptographic algorithms.
5.3
Functional Description
5.3.1
Programming Model
The CAU is an instruction-level coprocessor. It has a dedicated register file, a specialized ALU, and
specialized units for performing cryptographic operations. The CAU design uses a simple, flexible
accumulator-based architecture. Most commands, including load and store, can specify any register in the
register file. Some cryptographic operations work with specific registers.
5.3.2
Coprocessor Instructions
Operation of the CAU is controlled via standard ColdFire coprocessor load (cp0ld) and store (cp0st)
instructions. The CAU has a dedicated register file accessed using these instructions. The load instruction
loads CAU registers and specifies CAU operations. The store instruction stores CAU registers. The
example assembler syntax for the CAU is:
cp0ld.l
<ea>,<CMD>
; coprocessor load
cp0st.l
<ea>,<CMD>
; coprocessor store
The <ea> field specifies the source operand (operand1) for load instructions and destination (result) for
store instructions. The basic ColdFire addressing modes {Rn, (An), -(An), (An)+, (d16,An)} are supported
for this field. The <CMD> field is a 9-bit value that specifies the CAU command for an instruction.
shows how the CAU supports a single command (
STR
) for store instructions and 21 commands
for the load instructions. The CAU only supports longword operations. A CAU command can be issued
every clock cycle.
Register
code:
0x2 (CA0)
0x3 (CA1)
0x4 (CA2)
0x5 (CA3)
0x6 (CA4)
0x7 (CA5)
Access: Read/write
via CAU commands
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R
CAn
W
Reset 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 5-4. CAU General Purpose Registers (CAn)
Table 5-4. CAn Field Descriptions
Field
Description
31–0
CAn
General purpose registers. Used by the CAU commands. Some cryptographic operations work with specific
registers.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
