Freescale Semiconductor MCF5480 - Manual (Page 676)

MCF548x Reference Manual, Rev. 3
22-74 Freescale Semiconductor
22.14.2.2 Statically Assigned DEU
When statically assigned, it can be assumed that no other crypto-channel will access the DEU in between
descriptors. Therefore, in this usage mode, the context remains within the DEU. The DEU is programmed
with the particular mode of operation at the time of context-load. The following descriptors have been
optimized for encryption/decryption of multiple data packets per context load.
Table 22-59 shows the first descriptor that loads a key and optional context (IV) into the DEU, then
performs the initial cipher.
Table 22-60 lists the specific descriptors that use the format shown in Table 22-59 .
0x20300010 ECB Triple DES Encrypt
0x20200010 ECB Triple DES Decrypt
Table 22-59. First Descriptor for a Statically Assigned DEU
Field Name Value/Type Description
Header Table 22-60 Header common to several descriptors (TYPE 0001)
LEN_1 Length (not used) NULL
PTR_1 Pointer (not used) NULL
LEN_2 IV Length Number of bytes of IV to be written (always 8) (optional)
PTR_2 IV Pointer Pointer to context to be written into DEU (optional)
LEN_3 Key Length Number of bytes in Key (8 for SDES; 16 or 24 or TDES)
PTR_3 Key Pointer Address of Key
LEN_4 Data In Length Number of bytes of data to be ciphered (multiple of 8)
PTR_4 Data In Pointer Address of data to be ciphered
LEN_5 Data Out Length Bytes of output data (should be equal to length of data in)
PTR_5 Data Out Pointer Address to write output data
LEN_6 IV Out Length NULL
PTR_6 IV Out Pointer NULL
LEN_7 MAC Out Length NULL
PTR_7 MAC Out Pointer NULL
PTR_NEXT Next Descriptor Pointer Pointer to next data packet descriptor
Table 22-60. Typical Header Values for First Static DEU Descriptor Format
Header Value E/C S/T E/D
0x20500010 CBC Single DES Encrypt
0x20400010 CBC Single DES Decrypt
Table 22-58. Typical Header Values for Dynamic DEU Descriptor Format (Continued)
Header Value E/C S/T E/D