Freescale Semiconductor MCF5480 - Manual (Page 668)

MCF548x Reference Manual, Rev. 3
22-66 Freescale Semiconductor
The middle (and multiple subsequent) descriptors contains length/pointer pairs to the remaining data to be
permuted. Table 22-47 shows the format for a TYPE 0001 data packet descriptor that encrypts or decrypts
a block of data. Since the context and keys were loaded into the EU by a previous data packet descriptor
the LEN/PTR2 and LEN/PTR3 pairs are both NULL.
The final descriptor reads, permutes, and writes the final block of data, and outputs any context that needs
to be preserved for later use. Table 22-48 shows the format for a TYPE 0001 data packet descriptor that
encrypts or decrypts the final block of data and then optionally unloads the context.
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 22-47. Middle Static Descriptor Example
Field Name Value/Type Description
Header 0xXXXX_XX1X TYPE 0001
LEN_1 Length (not used) NULL
PTR_1 Pointer (not used) NULL
LEN_2 IV Length NULL
PTR_2 IV Pointer NULL
LEN_3 Key Length NULL
PTR_3 Key Pointer NULL
LEN_4 Data In Length Number of bytes to be encrypted/decrypted
PTR_4 Data In Pointer Address of data to be encrypted/decrypted
LEN_5 Data Out Length Bytes to be written (should be equal to length of data in)
PTR_5 Data Out Pointer Address where final data is written
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 22-48. Final Static Descriptor Example
Field Name Value/Type Description
Header 0xXXXX_XX1X TYPE 0001
LEN_1 Length (not used) NULL
Table 22-46. First Static Descriptor Example (Continued)
Field Name Value/Type Description