
Philips Semiconductors
Preliminary specification
PDI1394L40
1394 enhanced AV link layer controller
2000 Dec 15
25
12.6
The Asynchronous Packet Interface
The PDI1394L40 provides an interface to asynchronous data packets through the registers in the host interface. The format of the
asynchronous packets is specified in the following sections.
12.6.1
Reading an Asynchronous Packet
Upon reception of a packet, the packet data is stored in the appropriate receive FIFO, either the Request or Response FIFO. The location of the
packet is indicated by either the RREQQQAV or RRSPQAV status bit being set in the Asynchronous Interrupt Acknowledge (ASYINTACK)
register. The packet is transferred out of the FIFO by successive reads of the Asynchronous Receive Request (RREQ) or Asynchronous
Receive Response (RRSP) register. The end of the packet (the last quadlet) is indicated by either the RREQQLASTQ or RRSPQLASTQ bit set
in ASYINTACK. Attempting to read the FIFO when either RREQQQAV bit or RRSPQQAV bit is set to 0 (in the Asynchronous RX/TX interrupt
acknowledge, ASYINTACK, register) will result in a queue read error.
12.6.2
Link Packet Data Formats
The data formats for transmission and reception of data are shown below. The transmit format describes the expected organization for data
presented to the link at the asynchronous transmit, physical response, or isochronous transmit FIFO interfaces.
12.6.2.1
Asynchronous Transmit Packet Formats
These sections describe the formats in which packets need to be delivered to the queues (FIFOs) for transmission. There are four basic formats
as follows:
ITEM
FORMAT
USAGE
TRANSACTION CODE
(tCode)
1
No packet data
Quadlet read requests
4
1
No-packet data
Quadlet/block write responses
2
Quadlet write requests
0
2
Quadlet packet
Quadlet read responses
6
Block read requests
5
Block write requests
1
Block read responses
7
3
Block Packet
Lock requests
9
Lock responses
Bhex
Asynchronous streams
Ahex
4
Unformatted transmit
Concatenated self-ID / PHY packets
Ehex
Each packet format uses several fields (see names and descriptions below). More information about these fields (not the format) can be found
in the 1394 specification. Grey fields are reserved and should be set to zero values.