HT80C51 Datasheet, PDF (86/132 Pages) List of Unclassifed Manufacturers – User Manual Document Information

Handshake Solutions
HT80C51 User Manual
Peripheral Modules – Triple-DES Converter
Sometimes the text is in a different (reversed) byte order. Then following sequence can be used:
; Store key in KEY0
MOV DKEY, #B8h
MOV DKEY, #B7h
MOV DKEY, #B6h
MOV DKEY, #B5h
MOV DKEY, #B4h
MOV DKEY, #B3h
MOV DKEY, #B2h
MOV DKEY, #B1h
MOV DCON, #00h
(the byte order of the keys cannot be changed)
; Write plain text into DTXT (reversed order)
MOV DTXT, #3Dh
MOV DTXT, #9Dh
MOV DTXT, #3Fh
MOV DTXT, #A9h
MOV DTXT, #FCh
MOV DTXT, #8Ah
MOV DTXT, #D3h
MOV DTXT, #37h
MOV DCON, #3
; reverse byte order
; Invoke a single-DES encrytion
MOV DCON, #4
; the generated cipher text is F64E59B5B5A36506
; Reading the result (reversed order)
MOV DCON, #3
; reverse byte order for read-out
MOV R7, DTXT
MOV R6, DTXT
MOV R5, DTXT
MOV R4, DTXT
MOV R3, DTXT
MOV R2, DTXT
MOV R1, DTXT
MOV R0, DTXT
; will result with value 06h in R0, 65h in R1, etc.
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© Philips Electronics N.V. 2005