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Handshake Solutions
HT80C51 User Manual
Peripheral Modules – Triple-DES Converter
Page 82 of 132
© Philips Electronics N.V. 2005
5.8.
Triple-DES Converter
DES stands for `Data Encryption Standard’ and is a widely used standard for enciphering and deci-
phering blocks of data. This coprocessor can autonomously do a complete single- or triple- DES en-
cryption or decryption.
Features:
•
two 56bit key registers
•
64bit text register for encryption and decryption
•
single DES encryption
•
single DES decryption
•
triple DES encryption
•
triple DES decryption
5.8.1.
Options
The triple-DES converter can be selected (ordered) by using option HT80C51_DES .
5.8.2.
Special function registers (DCON DKEY DTXT)
DCON
DES control register (write only)
addr = C0H
reset value = XX
bits
7
6
5
4
3
2
1
0
-
-
-
-
-
DCMD
bit
symbol
Function
DCON.7
DCON.6
DCON.5
DCON.4
DCON.3
-
reserved bits
write always 0, read 0
DCON.2
DCON.1
DCON.0
Command for triple DES-converter. For a list of commands, see table
below.
The DCON register is write-only. The value, which is written into DCON, determines the
command for the triple-DES converter. This command is started immediately after DCON
has been written.
DCMD
command description
0
Store key in KEY0
1
Store key in KEY1
2
Swap KEY0 and KEY1
3
Reverse the order of bytes in
text register
4
Single-DES encryption
5
Single-DES decryption
6
Triple-DES encryption
7
Triple-DES decryption
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