Host Coalescing Control Registers
BCM5718 Programmer’s Guide
Broadcom
®
January 29, 2016 • 5718-PG108-R
Page 413
Host Coalescing Control Registers
The Host Coalescing Control Registers are responsible for pacing the rate at which the NIC updates the host's
transmit and receive buffer descriptor ring indices. Although the host produces and receives frames in one or
more buffer descriptors, the Host Coalescing state machine always updates the host on frame boundaries.
Additionally, the Host Coalescing state machine regulates the rate at which the statistics are updated in host
memory.
All registers reset are core reset unless specified.
Host Coalescing Mode Register (offset: 0x3C00)
Name
Bits
Access
Default
Value
Description
Reserved
31:13
RO
0
–
No Interrupt on DMAD Force
12
RW
–
When set, the COAL_NOW bit of the buffer
descriptor may be set to force a status block
update without a corresponding interrupt.
No Interrupt on Force update 11
RW
–
When set, writing the Coalesce Now bit will
cause a status without a corresponding interrupt
event.
Reserved
10
RO
0
When set, the TX Host Coalescing Tick counter
initializes to the idle state and begins counting
only after a transmit BD event is detected.
Clear Ticks Mode on Rx
9
RW
–
When set, the RX Host Coalescing Tick counter
initializes to the idle state and begins counting
only after a receive BD event is detected.
Status Block Size
8:7
RW
–
Status Block Size for partial status block updates
• 00: Full status block
• 01: 64 byte
• 10: 32 byte
• 11: Undefined
MSI Bits
6:4
RW
1
The least significant MSI 16-bit word is
overwritten by these bits. Defaults to 0.
Coalesce Now
3
RW
0
If set, Host Coalescing updates the Status Block
immediately and sends an interrupt to host. This
is a self-clearing bit. (For debug purpose only.)
Attn Enable
2
RW
–
When this bit is set to 1, an internal attention is
generated when an error occurs.
Enable
1
RW
–
This bit control whether the Host Coalescing
state machine 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.
Reset
0
RW
–
When this bit is set to 1, the Host Coalescing
state machine is reset. This is a self-clearing bit.