pnx1500 NXP Semiconductors, pnx1500 Datasheet - Page 725

• 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
Figure 10: Real-time/non-real-time transmit example
TxRt descriptors
Tx descriptors
Block zone
Tx clk cycles 0
LAN
Expired
P1
P2
P3
50
PRT1@90,
Real-time/non-real-time example
Figure 10
Prt2@110,
In this example initially both transmission queues have three descriptors; the first
packet in the real-time queue must be transmitted at time-stamp 90, the second
packet must be transmitted at time-stamp 110, and the third packet must be
transmitted at time-stamp 260. The packets in the non-real-time queue will be
transmitted as soon as possible.
In this example the BlockZone register is set to 30 time-stamp cycles.
After the device driver has set up the descriptors at time-stamp 50, the LAN100 starts
transmission. The initial real-time packet need not be transmitted yet, so a packet
from the non-real-time queue is transmitted first. During transmission of the
non-real-time packet, the time-stamp of the first real-time packet expires, and the
real-time packet will be transmitted as soon as transmission of the non-real-time
packet completes.
After transmitting the first real-time packet, the time-stamp of the second real-time
packet expires, and the transmission of the second real-time packet commences as
soon as the first real-time packet completes transmission.
After sending the second real-time packet, no new packets are sent out, since the
time-stamp is within the range of the block zone of the third real-time packet. As soon
as the Time-stamp Counter passes the packet’s time-stamp, the third real-time packet
is transmitted.
After completing transmission of the third real-time packet, the real-time queue is
empty, and the remaining non-real-time packets are transmitted as soon as possible.
Prt3@260
P1
100
shows an example of real-time and non-real-time traffic.
Prt1
150
Rev. 3 — 17 March 2006
PRT2@110,
Prt3@260
Prt2
Chapter 23: LAN100 — Ethernet Media Access Controller
200
250
P2
P3
Prt3@260
300
Prt3
350
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
P2
PNX15xx Series
400
P3
P3
450
500
23-56