pnx1500 NXP Semiconductors, pnx1500 Datasheet - Page 724

• Manufacturer Part Number: pnx1500
• Description: Pnx15xx Series Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX15XX_SER_3
Product data sheet
(because the GlobalTimeStamp counter wraps around 0), packets with time-stamps
that are late are only sent out when the difference between the time-stamp of the
packet and the local time-stamp of the time-stamp generator is less than half the total
time-stamp range , that is, less than 2
packet will not be transmitted, and the packet and all other packets in the real-time
descriptor list must wait until the value of the time-stamp generator wraps around to
its time-stamp value, or until software removes such a “stuck” packet by soft resetting
the Transmit Datapath.
The register BlockZone can be used to specify a time period before a transmit
time-stamp value during which no new transmission of non-real-time packets can be
started. This can help to free up the Ethernet wire for the impending real-time packet.
The unit of time of the BlockZone register is equal to the unit of time of the time-stamp
generator.
In pseudo-code, the real-time/non-real-time arbitration proceeds as follows:
If a non-real-time packet is still occupying the transmit logic when the time-stamp
moment of a real-time packet is reached, then the packet will be transmitted as soon
as the non-real-time packet has finished. When the value in BlockZone is 0, the
BlockZone mechanism is disabled.
Apart from using time-stamps for real-time transmission, the LAN100 also reports
back to software the actual moment that packets are received or transmitted, as
specified in
diff[31:0] = GlobalTimeStamp[31:0]
bs[31:0] = GlobalTimeStamp[31:0] + BlockZone[31:0]
if (!diff[31]) // is GlobalTimeStamp > descriptor time-stamp?
else if (!bs)
else
- TxRtDescriptor.timeStamp[31:0];
- TxRtDescriptor.timeStamp[31:0]
// True
// If possible, issue TxRt packet
// We are in the BlockZone, so do not issue
// If possible, issue Tx packet
Section
Rev. 3 — 17 March 2006
5.7.
Chapter 23: LAN100 — Ethernet Media Access Controller
31
. If the difference is more than 2
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX15xx Series
31
, then the
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