Broadcom BCM5722 - BCM5757, BCM5754, BCM5787 Only; Buffer Manager Mode Register (Offset 0 X4400); Table 298: Buffer Manager Mode Register (Offset 0 X4400); Table 299: Buffer Manager Status Register (Offset 0 X4404)-BCM5722, BCM5755, BCM5755 M, BCM5756 M

Programmer’s Guide BCM5722
10/15/07
Broadcom Corporation
Document 5722-PG101-R Buffer Manager Control Registers Page 306
BUFFER MANAGER MODE REGISTER (OFFSET 0X4400)
BUFFER MANAGER STATUS REGISTER (OFFSET 0X4404)
Table 298: Buffer Manager Mode Register (Offset 0x4400)
Bit Field Description Init Access
31 TXFIFO Underrun
Prevention Enable
• 1 = Enable the EMAC TXFIFO underrun prevention during LSO
offload operation. It will change the arbitration algorithm of TXMBUF
read requests to round-robin among CPU, PCIe, RDMA and
TXMAC. When TXFIFO is almost empty, RDMA will hold its request
till TXFIFO is not almost empty.
• 0 = Disable the EMAC TXFIFO underrun prevention during LSO
offload operation. The arbitration algorithm of TXMBUF read
requests will be priority-based among CPU, PCIe, RDMA and
TXMAC. RDMA will ignore TXFIFO almost empty alert.
0x1 R/W
Reserved (BCM5906
only)
–0x0RO
30:6 Reserved – 0 RO
5 Reset RXMBUF Ptr When this bit is set, it will cause the RXMBUF allocation and
deallocation pointer to reset back to the RXMBUF base. It will also
cause the RXMAC to drop the preallocated MBUF and request a new
one.
0R/WC
4 MBUF Low Attn Enable MBUF Low Attn Enable MBUF low attention enable. – R/W
3 BM Test Mode Buffer Manager Test Mode. Must be set to 0 for normal operation. – R/W
2 Attn_Enable When this bit is set to 1, an internal attention is generated when an error
occurs.
–R/W
1 Enable This bit controls whether the Buffer Manager is active or not. When set
to 0 it completes the current operation and cleanly halts. Until it is
completely halted, it remains one when read.
–R/W
0 Reset When this bit is set to 1, the Buffer Manager state machine is reset. This
is a self-clearing bit.
–R/W
Note: This register is not applicable to the BCM5906 device.
Table 299: Buffer Manager Status Register (Offset 0x4404)—BCM5722, BCM5755, BCM5755M, BCM5756M,
BCM5757, BCM5754, BCM5787 Only
Bit Field Description Init Access
31:5 BM Test Mode – RO
4 MBUF Low Attn MBUF low attention status RO
3 Reserved – RO
2 Error Buffer Manager error status RO
1:0 Reserved – 0 RO