Host Controller Data Manual

4–41

4.43 Isochronous Receive Context Match Register

The isochronous receive context match register is used to start an isochronous receive context running on a specified

cycle number, to filter incoming isochronous packets based on tag values, and to wait for packets with a specified

sync value. The n value in the following register addresses indicates the context number (n = 0, 1, 2, 3). See

Table 4–31 for a complete description of the register contents.

Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

Name Isochronous receive context match

Type R/W R/W R/W R/W R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W

Default X X X X 0 0 0 X X X X X X X X X

Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Name Isochronous receive context match

Type R/W R/W R/W R/W R/W R/W R/W R/W R R/W R/W R/W R/W R/W R/W R/W

Default X X X X X X X X 0 X X X X X X X

Type: Read/Write, Read-only

Offset: 410Ch + (32 * n)

Default: XXXX XXXXh

Table 4–31. Isochronous Receive Context Match Register Description

BIT FIELD NAME TYPE DESCRIPTION

31 tag3 R/W If this bit is set, then this context matches on iso receive packets with a tag field of 11b.

30 tag2 R/W If this bit is set, then this context matches on iso receive packets with a tag field of 10b.

29 tag1 R/W If this bit is set, then this context matches on iso receive packets with a tag field of 01b.

28 tag0 R/W If this bit is set, then this context matches on iso receive packets with a tag field of 00b.

27–25 RSVD R Reserved. Bits 27–25 return 0s when read.

24–12 cycleMatch R/W

Contains a 15-bit value, corresponding to the low-order two bits of cycleSeconds and the 13-bit

cycleCount field in the cycleStart packet. If isochronous receive context control register (see Section

4.41) bit 29 (cycleMatchEnable) is set, then this context is enabled for receives when the two low-order

bits of the bus isochronous cycle timer register (OHCI offset F0h, see Section 4.31) cycleSeconds field

(bits 31–25) and cycleCount field (bits 24–12) value equal this (cycleMatch) field value.

11–8 sync R/W

This field contains the 4-bit field which is compared to the sync field of each iso packet for this channel

when the command descriptor w field is set to 11b.

7 RSVD R Reserved. Bit 7 returns 0 when read.

6 tag1SyncFilter R/W

If this bit and bit 29 (tag1) are set, then packets with tag 01b are accepted into the context if the two most

significant bits of the packets sync field are 00b. Packets with tag values other than 01b are filtered

according to tag0, tag2, and tag3 (bits 28, 30, and 31, respectively) without any additional restrictions.

If this bit is cleared, then this context matches on isochronous receive packets as specified in

bits 28–31 (tag0–tag3) with no additional restrictions.

5–0 channelNumber R/W

This 6-bit field indicates the isochronous channel number for which this isochronous receive DMA

context accepts packets.