DS33X81+ Maxim Integrated Products, DS33X81+ Datasheet - Page 220

• Manufacturer Part Number: DS33X81+
• Description: IC MAPPING ETHERNET 256CSBGA
• Manufacturer: Maxim Integrated Products

Specifications of DS33X81+

• Applications: Data Transport
• Interface: Parallel/Serial
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Package / Case: 256-CSBGA
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Register Name:
Register Description:
Register Address:
191h:
Default
190h:
Default
Bits 0-12: LAN Queue Watermark [LQW 13-1] This register specifies the Watermark Threshold that is used to
trigger a LAN Pause control frame. One value is used for all 16 queues (each queue is independently enabled and
tested). The value from this register is multiplied by 64 to determine the minimum number of bytes available in each
DDR SDRAM LAN Queue after Flow Control (or LAN Queue Watermark Interrupt) is triggered. The maximum valid
value is decimal 8191, which designates that a minimum of 8191 x 64 bytes = 524,224 bytes can be stored after
the watermark is reached. The lowest valid setting is decimal 3, or a minimum of 192 bytes available when flow
control is triggered.
The purpose of the LQW setting is to prevent data loss due to queue overflow. The LQW setting is independent of
the CIR Policing function that monitors the rate at which data is received irrespective of the fill level of the queue.
For applications with maximum packet Length < 2049 and with a short Ethernet PHY transmission distance (< 25
meters) it is recommended that the LQW be set to a minimum value of 57.
For applications that include a long Ethernet PHY transmission distance the LQW setting can be increased. For
GbE applications the LQW value can be increased by 1 for each additional 88 meters (up to LQW = 8191 or
715km). For 100Mbps each incremental step will support 880 meters (at 100Mbps there is less/slower data on the
transmission line). For 10Mbps each incremental step will support 8,800 meters. It is recommended that the user
verify the LQW setting in long Ethernet transmission line applications.
Rev: 063008
________________________________________________ DS33X162/X161/X82/X81/X42/X41/X11/W41/W11
LQW-8
Bit 15
Bit 7
0
0
-
LQW-7
Bit 14
Bit 6
0
0
-
AR.LQW
LAN Queue Watermark
190h
LQW-6
Bit 13
Bit 5
0
0
-
LQW-13
LQW-5
Bit 12
Bit 4
0
0
LQW-12
LQW-4
Bit 11
Bit 3
0
0
LQW-11
LQW-3
Bit 10
Bit 2
0
0
LQW-10
LQW-2
Bit 9
Bit 1
0
0
220 of 375
LQW-9
LQW-1
Bit 8
Bit 0
0
0