Broadcom BCM5722 - Table 7: BCM5906 Status Block; Table 8: ISO Send BD

BCM5722 Programmer’s Guide
10/15/07
Broadcom Corporation
Page 23 Transmit Data Path Document 5722-PG101-R
• 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:
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:
• 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.
Table 7: BCM5906 Status Block
Offset 31 15
0x00 Status Word –
0x04 Unused –
0x08 Receive Standard Consumer Index Unused
0x0C Unused –
0x10 Data Send BD Consumer Index Receive Return BD Producer Index
0x14 ISO Send BD Consumer Index Unused
Table 8: ISO Send BD
Offset 31 15
0x00 Host Address –
0x04 – –
0x08 Len Flags
0x0C Launch time VLAN tag
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).