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section level 1 1
figure bi level 1
table_big level 1
restart lowapp ARestart oddapp: ARestarts for autonumbers that do not restart in
each chapter. figure bi level 1, reset table_big level 1, reset chap_big level 1, reset1
Lowapp Alwbox restart evenap:A1app_big level 1, resetA figure_ap level 1, reset
table_ap level 1, reset figure level 1, reset Figure 1. table level 1, reset Table 1.
these restarts oddbox reset: 1evenbox reset: 1must be in the header frame of
chapter 1. a:ebx, l 1 resetA a:obx:l 1, resetA a:bigbx level 1 resetA a:ftr level 1 resetA
c:ebx, l 1 reset1 c:obx:l 1, reset1 c:bigbx level 1 reset1 c:ftr level 1 reset1
Reminders for autonumbers that need to be restarted manually (first instance will
always be 4) let_in level 1: A. B. C. letter level 1:A.B.C. num level 1: 1. 2. 3.
num_in level 1: 1. 2. 3. rom_in level 1: I. II. III. roman level 1: I. II. III. steps level 1:
1. 2. 3.
1
GFK-0827
Chapter 1 Introduction
This chapter is an introduction to a method of CPU Redundancy for the Series 90-70
Programmable Logic Controller which is referred to as the Hot Standby CPU
Redundancy product.
The contents of this chapter provide:
a basic description of what Hot Standby CPU Redundancy is;
tells what it does for you - the user;
provides a basic description of the components of the Hot Standby CPU
Redundancy system;
provides a basic description of how a system is configured using the Logicmaster
90-70 programming software configurator function;
lists certain restrictions that you must be aware of;
and defines terminology unique to this product.
Note
For those who are not familiar with the various redundancy alternatives
which may be applied to a Series 90-70 PLC system, please refer to
Appendix A before proceeding with this chapter. For those who are familiar
with those redundancy alternatives please proceed with the dicussion of the ’Hot
Standby CPU Redundancy Product” below.
Hot Standby CPU Redundancy Product
CPU Redundancy for the Series 90-70 Programmable Logic Controller provides a
method of allowing a critical application or process to continue operating if a failure
occurs in any single component. The CPU Redundancy system described in this guide
is the Hot Standby CPU Redundancy product. A Hot Standby CPU Redundancy system
consists of two CPUs connected to one or more Genius I/O buses. Each PLC is
configured as either Primary or Secondary. The Primary PLC is the preferred PLC and