Datasheet

4–13
Table 4–6. Isochronous-Receive Functions
FIELD NAME DESCRIPTION
PacCom Packet complete. When PacCom = 1, the current block of data is the last one for the packet.
When PacCom = 0, the current block of data is just another block of the current packet.
spd The spd field indicates the speed at which the current packet is to be sent (00 = 100 Mbits/s,
01 = 200 Mbits/s, and 10 = 400 Mbits/s, and 11 is undefined).
WriteCount WriteCount indicates the number of data quadlets in the packet.
errCode The errCode field indicates whether the current packet has been received correctly. The
possibilities are complete, DataErr, or CRCErr, and have the same encoding as the corresponding
acknowledge codes (See Table 6–13 of the IEEE 1394-1995 standard).
dataLength The dataLength field indicates the number of bytes in the current packet.
TAG The TAG field indicates the format of data carried by isochronous packet (00 = formatted, 01 – 11
are reserved).
chanNum The chanNum field contains the channel number with which this data is associated.
tCode The tCode field carries the transaction code for the current packet (tCode = Ah).
sy The sy field carries the transaction layer-specific synchronization bits.
isochronous data The isochronous data field has the data to be sent with the current packet. The first byte of data
must appear in byte 0 of the first quadlet of this field. The last quadlet should be padded with zeros.
4.5 Snoop Receive
The format of the snoop data is shown in Figure 4–19. The receiver module can be directed to receive any
and all packets that pass by on the serial bus. In this mode, the receiver presents the data received to the
receive-FIFO interface.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
snooped_data
spd SnpStattCodeWrite CountackSnpd 1 1
Reserved
NOTES: A. Bit 11 (PacCom)=1
B. Bit 12 (EnSp) = 1. This is bit 0 of the diagnostic register.
Figure 4–19. Snoop Format
Table 4–7. Snoop Functions
FIELD NAME DESCRIPTION
ackSnpd Acknowledge snooped. This field indicates the acknowledge seen on the bus after the packet is
received.
spd This field indicates the speed at which this packet was sent (00 = 100 Mbits/s, 01 = 200 Mbits/s,
and 10 = 400 Mbits/s, and 11 is undefined).
WriteCount WriteCount indicates the number of data quadlets in the packet.
tCode The tCode field is the transaction code for the current packet (See Table 6–10 of the IEEE
1394-1995 standard).
SnpStat This field indicates whether the entire packet snooped was received correctly. A value equal to the
ack_complete acknowledge code indicates complete reception. This field has the same encoding
as the corresponding acknowledge codes (See Table 6–13 of the IEEE 1394-1995 standard).
snooped_data This field contains the entire packet received or as much as could be received into the GRF.