Data Sheet

Ethernet Controller I210 —Inline Functions
318
7.2.7.5.2 Data Transmission Credit Calculation
Definition and description of parameters
IdleSlope - The Idle slop of an SR queue defines the amount of credit accumulation (per byte) while the
queue is blocked from transmission
SendSlope - The Send slop of an SR queue defines the amount of credit consumption (per byte) and is
calculated by the formula SendSlope = IdleSlope - LinkRate
HiCredit - The HiCredit of an SR queue defines the maximum credit accumulation for that queue
Credit calculation pseudo code:
For each Q[i]
If Transmit
Credit = Credit – SendSlope
If !Transmit
If Q[i]QuFrm = 0
Credit = 0
Else If Credit + IdleSlope > HiCredit
Credit = HiCredit
Figure 7-12. Data Transmission Arbitration Operation for TransmitMode = Qav
Start
QN = 0
Q[QN].QueueFrames > 0
?
QN = QN + 1
QN > 3
?
No
Yes
No
Yes
Q[QN].Mode = ?
SP SR
[Q[QN].LnchTime reached
or (DataTranTIM =0)] &&
[(Q[QN].Credits >= Zero)
or (DataTranARB=0)]
?
No
Yes
Send a Packet
from Q[QN]
SP_WAIT_SR &&
Q[0,1].LnchTime minus
MAX_TPKT_SIZE
reached
?
Yes
No
(Qav)
(Best
Effort)