Table 7: Bcm5906 Status Block; Table 8: Iso Send Bd - Broadcom BCM5722 Programmer's Manual

BCM5722
Offset 31
0x00 Status Word
0x04 Unused
0x08 Receive Standard Consumer Index
0x0C Unused
0x10 Data Send BD Consumer Index
0x14 ISO Send BD Consumer Index
• The ISO packet launch time field will has been added to the upper 16 bits of offset 0xC in the ISO SBD, as shown in
Table 8:
Offset 31
0x00 Host Address
0x04 –
0x08 Len
0x0C Launch time
Bit 10 in the Flags field of the ISO SBD specifies that this packet is a transmit time sync packet (the local network clock
value is logged in register 0x0C28 when this packet transmits onto the wire).
Bit 13 of the BCM5906 ISO Send BD is the BD_FLAG_LT_WRAP bit. It is to be set in the first Send BD only, and only if
the launch time of the packet is smaller than that of the previous packet and the frame should not be transmitted
immediately.
Bit 14 of the BCM5906 ISO Send BD is the BD_FLAG_TIMER_INIT bit. It is to be set if the local launch time wrap bit
(bit 13) needs to be cleared immediately. This can be used for a packet that is the beginning of a new ISO stream.
• Register 0x0C20 is the ISO Packet Transmit Support register. Bits 1:0 identify the decision scheme used by the Data
SDI to make RDMA requests:
00 Unconditionally
01 Throughput calculation method
10 De-pipeline method
11 Undefined
Note: For BCM5906/BCM5906M, revisions A0, A1, and A2 use only decision scheme 10 (0x2).
• Register 0x0C24 is the Local Network Time Clock register. It is a free-running, increment-by-40 counter (it increments
every 40 ns, driven by 25-MHz clock). It can be updated (written) and read by software.
• Register 0x0C28 is the Logged Local Network Time register, which stores the time when the time-sync packet is
transmitted. It is read-only by software.
• Both tx and rx time-sync packet timestamps share the same timestamp register at offset 0xc28.
Page 23 Transmit Data Path

Table 7: BCM5906 Status Block

15
–
–
Unused
–
Receive Return BD Producer Index
Unused

Table 8: ISO Send BD

15
–
–
Flags
VLAN tag
Bro adco m C orp or atio n
Programmer's Guide
10/15/07
Document 5722-PG101-R