Philips Semiconductors
Preliminary specification
1394 enhanced AV link layer controller
PDI1394L40
Port Dir
Transmit
Receive
AVxREADY
Out
In
Description
The L40 is prepared to receive a byte. The attached device will not assert AVVALID for any cycle in which
AVxRDY is false.
The attached device is prepared to receive a byte. The L40 will not assert AVxVALID for any cycle in which
AVxREADY is false.
When the AV port is configured as a receiver, the AVxSYNC signal will be asserted as soon as the PDI1394L40 AVx port has an application
packet available for delivery (independent of AVxREADY) and will remain asserted until the first byte of the application packet is clocked from
the AV port.
12.2.4 Audio Support
The AV transmitter has some additional features to support some types of audio transport. These are enabled by setting bit 30 of ITXPKCTL
(0x020) to logic 1. At the rising edge of AVxFSYNC, a SYT time stamp will be generated and written into the SYT queue of the isochronous
transmitter. This stamp will point to a time in the future dictated by the following formula:
SYT[15:12] = CYCTM[15:12] + programmed SYT_DELAY value + 2
SYT[11:0] = CYCTM[11:0]
The additional delay of two cycles is specific to this AUDIO mode. The oldest SYT time stamp in the SYT queue will be sent first, but only when
accompanied by a data payload. Any pending SYT time stamp will be held until the next non-empty bus packet is sent. At the moment of
transmission, the SYT time stamp should at least point one cycle in the future. If it points to a time that is less than one cycle in the future, it will
be discarded.
The SYT queue in the isochronous transmitter can store 4 entries, the SYT queue in the isochronous receiver can store six entries. This
supports the case where an 8 kHz signal is applied to AVxFSYNC, and AUDIO = 1, and SYT_Delay = 2. Assuming there is data on every cycle,
the receiver will receive an SYT time stamp each cycle with the first SYT time stamp pointing just less than six cycles in the future. When the
SYT queue in the isochronous receiver is full, then the most recently received SYT time stamp is overwritten with the next arriving SYT time
stamp. If the queue should become full or contain a corrupted time stamp, the queue will automatically clear and indicate so by setting the
“SYTOVF” interrupt.
12.2.5 SY – Sync Support
This feature supports the 1394 digital camera specification. The state of this pin will be reflected in the SY bit (ITXCTL register 0x034) and will
be transmitted along with the isochronous data block that was entered with it. The intended use of this pin is to signal the start of a new frame of
video in the isochronous header section of the data payload. Similarly, the isochronous receiver will assert the AVxSY pin simultaneously with
the first byte of the isochronous bus packet in which the SY value was received.
AV DATA
AV SYNC
AV SY
SV01787
Figure 1. Behavior of SY signal at AV port of receiver
12.2.6 Programmable Buffer Memory
The PDI1394L40 maintains six distinct buffers that are highly configurable to optimize bandwidth capabilities. Buffers can be increased or
decreased from the default value by accessing the indirect address range of 0x100 through 0x1FC (INDADDR, 0x0F8). If the AV Layer is
configured to transmit or receive DVB compliant MPEG-2 type data, the default Isochronous (AV) buffer sizes are recommended. FIFO sizes
cannot be changed dynamically; after a FIFO size change, transmitters and receivers must be reset.
Buffers can be programmed with 64 quadlet (256 Byte) granularity. Minimum buffer size is 64 quadlets, maximum buffer size is limited to 11 kB.
The sum of all buffers cannot exceed 12K Bytes, or 3K Quadlets.
2000 Dec 15
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PHILIPS [ NXP SEMICONDUCTORS ]
