Allen-Bradley 1734-SSI, Руководство пользователя, Страница: 31 / 48

Rockwell Automation Publication 1734-UM007E-EN-P - October 2015 31
Set and Operate Your Module Chapter 4
Automatic Mode
The purpose of the Automatic mode is to provide a means of switching between
two comparator values without having to activate each comparator separately
through the configuration.
In Automatic mode, only the Both comparator control setting is active for
Comparator 1 and Comparator 2. There is no provision to choose between the
comparator control settings in Automatic mode.
In Automatic mode, you must first enter values for Comparator 1 and
Comparator 2 through the configuration. Enforce bit 3 of the Master Ack byte
(SCMP1) by setting it to 1. Make sure bit 4 of the Master Ack Byte (SCMP2) is
set to 0 when you enforce SCMP1.
Notice that C1ST is now 1, indicating that the Comparator 1 is active. When the
SSI sensor reaches the Comparator 1 value and the C1R bit is 1, enforce SCMP2
by setting it to 1.
Notice that C2ST is now 1, indicating that Comparator 2 is active. Also notice
that C1ST and C1R are now 0. When the sensor reaches the Comparator 2
value, C2R gets set to 1. You may now repeat the cycle by enforcing SCMP1
while setting SCMP2 to 0. Cancel Automatic mode by setting both SCMP1 and
SCMP2 to 0.
Other Module Features The Module Status word, consisting of Status Bytes 0 and 1, contains
information regarding module operation.
The DEC and INC bits, bits 2 and 3, respectively, of Status Byte 0, indicate
sensor count direction as the SSI sensor is in motion. Watch these bits change as
the SSI sensor changes direction. If the count is currently increasing, INC is 1.
When the count decreases, DEC is 1. If INC and DEC are both 0, the SSI sensor
is not in motion, or is moving very slowly. There are two green LEDs (INC and
DEC) on the front of the module, which also indicate the SSI sensor count
direction.
The lower bits of Status Byte 1 provide module troubleshooting information. If
the SPF (bit 0 of Status Byte 1) bit is 1, the SSI sensor power provided at the
module terminal block is shorted, or the SSI power is not present. This causes
incorrect SSI sensor data to be collected by the module.
Major module faults are indicated by the presence of the CCF and CCE bits, bits
1 and 2 respectively of Status Byte 1.If either of these bits is 1, you do not receive
correct SSI sensor data. Try resetting the module with a power cycle.
IMPORTANT
After setting SCMP2 to 1, set SCMP1 to 0. Setting them both to 0 at the same
time cancels Automatic mode.