2-2 Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide May 2000 GFK-1527A
2
Redundancy CPU
The redundancy CPUs have been designed specifically for Series 90-70 Hot Standby CPU
Redundancy applications.

Features

The Enhanced Hot Standby CPU supports floating point calculations, offers remote programmer
keyswitch memory protection, and has seven status LEDs. Operation of the CPU may be
controlled by the three-position RUN/STOP switch on the module, or remotely by an attached
programmer. Program and configuration data can be locked through software passwords or
manually by the memory protect keyswitch. When the key is in the protected position, a
programmer connected to the Bu s Tr an smitter Module can only change pr ogr am and configuration
data.
In a Hot Standby CPU Redundancy system, one CPU is configured as the Primary CPU and the
other as the Secondary CPU. The Prim ary unit and the Secondary unit must ea ch have a
Redundancy CPU installed in slot 1 of rack 0.
C
P
U
C
P
U
B
T
M
R
C
M
G
B
C
30
Secondary Unit Primary Unit
31
P
SP
S
B
T
M
R
C
M
G
B
C
Genius Bus
CGR935 Redundanc
y
C
ommunications Link
Redundanc
y
C
ommunications Link
CGR772
in these slots
or
Not all features of other Series 90-70 CPUs are available in redundancy models. See chapter 4 for
details.