
8201, 8202, 8203, 8204 Acceleration Processor Data Sheet, DS-0157-05
Page 107
Exar Confidential
4.2 Decode Operations Data Flow
4.2.1
Hash Engine before Encryption Engine
Figure 4-5 shows the data flow when the position of the Hash Engine is before the
Encryption engine and all four engines are enabled. The data flow is the reverse of the
“Hash Engine after Encryption Engine” encode operation.
1. First, the DMA fetches the encrypted, compressed data with padding, ENC (CMP +
Pad) & MAC, from the host according to the command structures, and sends the
data to processing channel 0 or processing channel 1.
2. In parallel, processing channels 0 and 1 begin to process the “ENC (CMP + Pad) &
MAC” data for separate commands.
3. The MAC value is sent to the Hash engine through the information bus, and the
“ENC (CMP + Pad)” data is sent to the Hash engine through the data bus. Please
4. The Hash engine calculates the MAC value of the “ENC (CMP + Pad)” data and
compares the result to the MAC value on information bus to determine whether the
input stream is valid, and also passes through the “ENC (CMP + Pad)” data to the
Encryption engine.
Figure 4-4. Encode Operation: Hash Engine after Encryption Engine