IBM eServer zSeries 900 Technical Guide

88 IBM eServer zSeries 900 Technical Guide

Figure 3-2 ESCON-to-parallel channel connection via 9034

For further information, see the following manuals:

򐂰

IBM zSeries Connectivity Handbook

, SG24-5444

򐂰

IBM System/360 and System/370 I/O Interface Channel to Control Unit Original

Equipment Manufacturer's Information

, GA22-6974

򐂰

zSeries 900 lnput/Output Configuration Program User’s Guide for IYP IOCP

, SB10-7029

򐂰

z/Architecture Principles of Operation

, SA22-7832

3.3 ESCON channel

Enterprise Systems CONnection (ESCON) is an integral part of z/Architecture for z900 and

the Enterprise Systems Architecture/390 (ESA/390) for earlier generation servers. ESCON

augments the previous S/370 parallel OEMI interface with the ESCON I/O interface

supporting new media and providing new interface protocols (see Figure 3-3). Unlike the

previous bus and tag cables and their multiple data and control lines, ESCON provides

bi-directional serial bit transmission, in which the communication protocol is implemented

through sequences of special characters and through formatted frames of characters.

Note: The IBM 9034 has been withdrawn from marketing.

An alternative product to the IBM 9034 is the Optica Technologies 34600 FXBT ESCON

Converter. More information can be found at:

http://www.opticatech.com/34600.asp

ESCON Converter

9034-001

CU

CU

Device

Device

Parallel

BUS and TAG

Cables

z900 server

ESCON

link

Chapter 3. Connectivity 89

Figure 3-3 ESCON connectivity

In contrast to the previous copper cables used by the parallel OEMI, ESCON utilizes fiber

optic cables for data transmission. These cables are 100 times lighter than the old bus and

tag cables, have substantially reduced bulk, have less loss and distortion, are immune to

electrical interference, and are free from signal skew.

ESCON modes

ESCON has a different topology of control unit and channel attachment compared with

parallel channel. ESCON control units can be connected directly to an ESCON channel

(point-to-point), or can be dynamically switched via an ESCON Director (Switched

point-to-point); see Figure 3-4 on page 90.

Tape

17 MBps

ESCON Links

ESCON

Channels

ESCON

Director

z900 server

z900 server

Disk

90 IBM eServer zSeries 900 Technical Guide

Figure 3-4 The ESCON native mode

The switching capabilities allow multiple connections between channels and control units

without requiring static (dedicated) physical connections. The point-to-point connections allow

physical changes to the I/O configuration concurrently with normal operations. Both

topologies are implemented by defining an ESCON channel as CNC using the Hardware

Configuration Definition (HCD).

In order to accommodate parallel channel-attached control units and devices, the ESCON

conversion mode allows communication from an ESCON channel to parallel

channel-attached control units operating in block multiplexer or byte multiplexer mode. This is

done through an IBM 9034 ESCON Converter; see Figure 3-5. The ESCON channel is

defined as CVC (block multiplexer mode) or CBY (byte multiplexer mode) using the HCD.

Figure 3-5 The ESCON conversion mode

ESCON channel-to-channel

ESCON offers an effective and price-competitive replacement for previous

channel-to-channel hardware. With ESCON channels, a user can communicate at channel

speed between servers without requiring extra hardware. “ESCON channel-to-channel” on

page 96 covers this connectivity in detail.

ESCON

CU & I/O

ESCON

CU & I/O

ESCON

CU & I/O

ESCD

ESCON point-to-point

ESCON Switched point-to-point

CNC

CNC

ESCON

Channels

ESCD

ports

ESCON

Converter

Model 1

T

Bus

Tag

Parallel

CU & I/O

Parallel

CU & I/O

Parallel

CU & I/O

up to 8 // CUs

ESCON conversion

CVC/CBY