IBM 3745 Series, Hardware Maintenance Reference

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Introduction
The Ethernet LAN subsystem (ESS) attaches a maximum of four Ethernet-type local area networks
(maximum of two when token-ring adapters are installed). It consists of up to two Ethernet LAN adapters
(ELA). Each adapter can attach up to two Ethernet-type LANs, through a media adapter unit (MAU) oper-
ating at 10 million bits per second (Mbps).
The Ethernet LAN adapter (ELA) can be installed in all 3745 models (configuration dependent).
Ethernet subsystem provides attachment to a carrier sense multiple access, with collision detection
(CSMA/CD).
System Environment
The ELA supports both Ethernet LAN Version 2 and IEEE 802.3 frames.
ELA Packaging
The handling and management of such a communication is achieved by an Ethernet LAN adapter (ELA)
made of two cards:
Ÿ
One communication scanner processor packaged on one card, the CSP card identical to those of the
high-speed scanner (HSS) but with a different CSP microcode load module (see “ELA Microcode
Description” on page 12-11).
Ÿ One Ethernet adapter card, the EAC card.
ELA is installed in HSS positions.
The ELA interface to the external equipment is a IEEE 802.3 15-pin D-type female AUI connector requiring
a slide latch on mounting connector. The ESS uses the tail gate location of the corresponding HPTSS.
For board and card locations, refer to the "Maintenance Information Procedures", SY33-2070.
The tail gate contains also a DC/DC converter, one per port, which provides
+ 12V DC with up to 500 mA per port. The + 12V DC supplies an external transceiver called media
access unit (MAU).
On the tail gate a green LED is On when the + 12 V DC is present on the corresponding J connector.
Use of MAUs
The performance of the Ethernet feature have been checked with a wide range of OEMs MAUs. Although
meeting the 802.3 standards, some MAUs are more sensitive than others to electromagnetic environment
and may degrade the box performance related to the noise margin.
: The MAU must be equipped with the
SQE-TEST (also called HEARTBEAT) function.
Chapter 12. Ethernet Subsystem (ESS)
12-5