LAN9353 Datasheet, PDF (215/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
TABLE 10-1: SPANNING TREE STATES (CONTINUED)
Port State
Hardware Action
Software Action
10 - Learning
00 - Forwarding
Received packets on the port are dis-
carded unless overridden.
Transmissions to the port are blocked
unless overridden.
Learning on the port is enabled.
The MAC Address Table should be programmed
with entries that the host CPU needs to receive
(e.g., the BPDU address). The Static and Age 1/
Override bits should be set.
The host CPU may send packets to the port in this
state. Only packets with STP override will be trans-
mitted.
Received packets on the port are for-
warded normally.
Transmissions to the port are sent nor-
mally.
Learning on the port is enabled.
The MAC Address Table should be programmed
with entries that the host CPU needs to receive
(e.g., the BPDU address). The Static and Age 1/
Override bits should be set.
The host CPU may send packets to the port in this
state.
10.3.6 INGRESS FLOW METERING AND COLORING
Hardware ingress rate limiting is supported by metering packet streams and marking packets as either Green, Yellow
or Red according to three traffic parameters: Committed Information Rate (CIR), Committed Burst Size (CBS) and
Excess Burst Size (EBS). A packet is marked Green if it does not exceed the CBS, Yellow if it exceeds to CBS but not
the EBS or Red otherwise.
Ingress flow metering and coloring is enabled via the Ingress Rate Enable field in the Switch Engine Ingress Rate Con-
figuration Register (SWE_INGRSS_RATE_CFG). Once enabled, each incoming packet is classified into a stream.
Streams are defined as per port (3 streams), per priority (8 streams) or per port & priority (24 streams) as selected via
the Rate Mode field in the Switch Engine Ingress Rate Configuration Register (SWE_INGRSS_RATE_CFG). Each
stream can have a different CIR setting. All streams share common CBS and EBS settings. CIR, CBS and EBS are
programmed via the Switch Engine Ingress Rate Command Register (SWE_INGRSS_RATE_CMD) and the Switch
Engine Ingress Rate Write Data Register (SWE_INGRSS_RATE_WR_DATA).
Each stream is metered according to RFC 2697. At the rate set by the CIR, two token buckets are credited per stream.
First, the Committed Burst bucket is incremented up to the maximum set by the CBS. Once the Committed Burst bucket
is full, the Excess Burst bucket is incremented up to the maximum set by the EBS. The CIR rate is specified in time per
byte. The value programmed is in approximately 20 ns per byte increments. Typical values are listed in Table 10-2.
When a port is receiving at 10 Mbps, any setting faster than 39 has the effect of not limiting the rate.
TABLE 10-2: TYPICAL INGRESS RATE SETTINGS
CIR Setting
0-3
4
5
6
7
9
12
19
39
Time Per Byte
80 ns
100 ns
120 ns
140 ns
160 ns
200 ns
260 ns
400 ns
800 ns
Bandwidth
100 Mbps
80 Mbps
67 Mbps
57 Mbps
50 Mbps
40 Mbps
31 Mbps
20 Mbps
10 Mbps
 2015 Microchip Technology Inc.
DS00001925A-page 215