Production Specification

07/03/02

B roa dcom Co rpo rat ion

Document

5802-DS03-405-R

Overview of Software Interface

The following figure shows an overview of the various structures and linkages used to forward packet/key setup data to the

chip. Fields indicated by an @ sign correspond to pointers. The # PKT field in the master command structure allows up to

entry in a master command buffer specify the start of a buffer chain into which output (encrypted or decrypted) data is written.

The master command structure is a single point of communication between the host CPU and the chip. Chip processing of

any number of packets is initiated by writing the address of a master command structure to the on-chip master command

address register (Master Command Register 1). The chip signals completion of processing by writing status information to

the flags entry at the beginning of the master command structure and by posting an interrupt per master command structure

(if enabled).

Figure 5:

Structures and Linkages Used to Forward Packet/Key Setup Data to Chip

Note

The NEXT@ field of the last output data buffer pointer is never used to access data for IPsec crypto/

authentication operations. This field instead contains the address of a buffer to which HMAC information

is written to or read from, if HMAC processing is specified for a given packet. For HMAC-MD5, the entire

16 bytes of hash result is written to the buffer. For HMAC-SHA1, the entire 20 bytes of hash result is written

to the buffer. For the IPsec HMAC-96, the software must discard the last four bytes of the data for HMAC-

MD5 and the last eight bytes of the data for HMAC-SHA1.

FLAGS, # PKT

CMD @

INPUT PKT @

INPUT PKT NEXT @

PKT LEN

CONTEXT

BUFFER FOR

PACKET #1

PACKET #1,

DATA BUF #1

PACKET #1,

DATA BUF #2

PACKET #1,

OUTPUT DATA

BUF #1

PACKET #1,

OUTPUT DATA

BUF #2

CONTEXT

BUFFER FOR

PACKET #2

OUTPUT PKT @

OUTPUT PKT NXT@

OUTPUT DATA LEN

DATA @

NEXT @

DATA @

NEXT @

MASTER

CMD

DATA LEN

DATA LEN

INPUT DATA LEN

INPUT PKT @

CMD @

INPUT PKT NEXT@

PACKET #2, DATA

BUF #1

PACKET #1,

HMAC DATA