Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 23: LAN100 — Ethernet Media Access Controller
12NC 9397 750 14321
Koninklijke Philips Electronics N.V. 2002-2003-2004. All rights reserved.
Product data sheet
Rev. 2 — 1 December 2004
23-17
This register is a byte address aligned to a word boundary (i.e., the two LSBs are fixed to 0). The register contains the
lowest address in the array of descriptors.
31:2
TxRtDescriptor
R/W
MSBs of real-time descriptor base address.
1:0
Offset 0x07 2134
-
0
Fixed to 0.
Real-time Transmit Status Base Address Register (TxRtStatus)
This register is a byte address aligned to a double word boundary (i.e., the three LSBs are fixed to 0). The register contains
the lowest address in the array of status words.
31:3
TxRtStatus
R/W
MSBs of real-time transmit status base address.
2:0
Offset 0x07 2138
-
0
Fixed to 0.
Real-time Transmit Number Of Descriptors Register (TxRtDescriptorNumber)
This register defines the number of descriptors in the descriptor array for which TxRtDescriptor is the base address. The
number of descriptors should match the number of statuse words. The register uses minus-one encoding, i.e., if the array
has 8 status elements, the value in the register should be 7.
31:16
-
-
Unused
15:0
TxRtDescriptorNumber
R/W
0
Number of descriptors in the descriptor array for which
TxRtDescriptor is the base address. The number of descriptors is
minus-one encoded.
Real-time Transmit Produce Index Register (TxRtProduceIndex)
Offset 0x07 213C
This register defines the descriptor that is going to be filled next by the software transmit driver. The transmit descriptor array
is empty as long as TxRtProduceIndex equals TxRtConsumeIndex. As soon as the array is not empty, the real-time transmit
hardware will start transmitting packets, if enabled. After a packet has been processed by software, software should
increment the TxRtProduceIndex, wrapping to 0 once TxRtDescriptorNumber has been reached. If the TxRtProduceIndex
equals TxRtConsumeIndex – 1, the descriptor array is full, and software should stop producing new descriptors until
hardware has transmitted some packets and updated the TxRtConsumeIndex.
31:16
-
-
Unused
15:0
TxRtProduceIndex
R/W
0
Index of the descriptor that is going to be filled next by the real-time
transmit software driver.
Real-time Transmit Consume Index Register (TxRtConsumeIndex)
Offset 0x07 2140
This register defines the descriptor that is going to be transmitted next by the hardware real-time transmit process. After a
packet has been transmitted, hardware increments the index, wrapping to 0 once TxRtDescriptorNumber has been
reached. If the TxRtConsumeIndex equals TxRtProduceIndex, the descriptor array is empty, and the transmit channel will
stop transmitting until software produces new descriptors.
31:16
-
-
Unused
15:0
TxRtConsumeIndex
RO
Index of the descriptor that is going to be transmitted next by the
real-time Transmit Datapath.
Transmit Block Zone Register (BlockZone)
Offset 0x07 2144
The BlockZone Register is only used in real-time/non-real-time arbitration mode, i.e., when the EnableQoS bit in the
Command register is deasserted. The BlockZone register defines a window before a real-time transmission time-stamp in
which no new non-real-time transmissions can be started, so as to free up the Ethernet for a pending real-time transmission.
The size of the BlockZone window in seconds is: BlockZone * T
Time-stamp Clock
No new non-real-time transfers will be started if: DescriptorTimeStamp < GlobalTimeStamp + BlockZone
The real-time transmission will start as soon as: DescriptorTimeStamp < GlobalTimeStamp.
31:16
-
-
Unused
Table 2: LAN100 Registers
…Continued
Bit
Symbol
Acces
s
Value
Description