Analog Devices ADSP-SC58 Series Hardware Reference Manual page 3079

Phase 2. Write the State Registers, (ARC4 Buffer) and SA Registers
All required fields of the SA record and state record must be written. The fields required depend on the operation.
The last field to be written is the
ing.
1. Write the required state record fields.
• ARC4 state
• IV
• Digest count
• State digest
2. Write the required SA record data.
3. To complete the SA record and state record, write the
Phase 3. Write the Source Packet Data and Read Result Packet Data
The packet engine has input and output buffers. If a source packet is smaller than the size of the input buffer, then
the packet can be written in one part. Otherwise, it must be written in multiple parts. The same applies to the out-
put data. If the result packet size is smaller than the size of the output buffer, then the packet can be read in one
part. Otherwise, it must be read in multiple parts.
An outbound packet that is smaller than the size of the input buffer can increase in size due to padding
NOTE:
and does not always fit in the output buffer. Conversely, an inbound packet that is larger than the size of
the input buffer can decrease in size, and due to de-padding, can fit in the output buffer. If the input buf-
fer becomes empty or the output buffer becomes full, the engine stalls.
Two following steps describe different situations:
• Source packet smaller than the size of the input buffer, start at step 1.
• Source packet larger than the size of the input buffer, start at step 3.
The host processor must follow these steps:
1. Write the source packet data. Write the full source packet to the input buffer. Go to step 4.
2. Write the input buffer count register (PKTE_INBUF_CNT) with the number of valid bytes that are written to
the input buffer. This value must correspond to the value in thePKTE_LEN.TOTLEN field of the command
descriptor rounded up to the next multiple of 4 bytes. Go to step 5 to check the packet engine status.
3. Write part of the source packet data. The PKTE_STAT.IBUFEMPTYCNT field indicates the amount of free
space in the input buffer. Programs write the number of bytes determined by the setting in the
PKTE_BUF_THRESH
resume where it ended the previous write operation. Do not write more than the buffer size at once. Go to step
4.
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
PKTE_SA_RDY register. This register triggers the packet engine to start process-
register. Write the (partial) source packet to the input buffer. The host processor must
PKTE_SA_RDY register.
PKTE Programming Model
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