DS33Z11 Maxim Integrated Products, DS33Z11 Datasheet - Page 60

• Manufacturer Part Number: DS33Z11
• Description: Network Controller & Processor ICs Ethernet Mapper Ethe rnet-Serial TDM Ethe
• Manufacturer: Maxim Integrated Products

Specifications of DS33Z11

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.19 Committed Information Rate Controller
The DS33Z11 provides a CIR provisioning facility. The CIR can be used restricts the transport of received MAC
data to a programmable rate. This is shown in
MAC to Transmit HDLC. This can be used for provisioning and billing functions towards the WAN. The user must
set the CIR register to control the amount of data throughput from the MAC to HDLC transmit. The CIR register is
in granularity of 500 kbps with a range of 0 to 52 Mbps. The operation of the CIR is as follows:
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The CIR block counts the credits that are accumulated at the end of every 125 ms
If data is received and stored in the SDRAM to be sent to the Serial Interface, the interface will request
the data if there is a positive credit balance. If the credit balance is negative, transmit interface does not
request data
New credit balance is calculated credit balance = old credit balance – frame size in bytes after the frame
is sent
The credit balance is incremented every 125 milliseconds by CIR/8
Credit balances not used in 250 milliseconds are reset to 0
The maximum value of CIR can not exceed the transmit line rate
If the data rate received from the Ethernet interface is higher than the CIR, the receive queue buffers will
fill and the high threshold watermark will invoke flow control to reduce the incoming traffic rate.
The CIR function is only available for software mode of operation only
CIR function is only available in data received at the Ethernet Interface to be sent to WAN. There is not
CIR functionality for data arriving from the WAN to be sent to the Ethernet Interface
Negative credits are not allowed, if there is not a credit balance, no frames are sent until there is a credit
balance again.
Figure
60 of 172
8-14. The CIR will restrict the data flow from the Receive