GE C30 Instruction Manual page 176

5.2 PRODUCT SETUP
The operand shall be configured to drive an output contact, user-programmable LED, or selected communication-based
output. Latching and acknowledging conditions - if required - should be programmed accordingly.
The CRC alarm function is available on a per-channel basis. The total number of direct input and output messages that
failed the CRC check is available as the
value.
• Message count and length of the monitoring window: To monitor communications integrity, the relay sends 1 message
per second (at 64 kbps) or 2 messages per second (128 kbps) even if there is no change in the direct outputs. For
example, setting the
64 kbps and 80 minutes at 128 kbps. If the messages are sent faster as a result of direct outputs activity, the monitor-
ing time interval will shorten. This should be taken into account when determining the
setting. For example, if the requirement is a maximum monitoring time interval of 10 minutes at 64 kbps, then the
ALARM CH1 MESSAGE COUNT
• Correlation of failed CRC and bit error rate (BER): The CRC check may fail if one or more bits in a packet are cor-
rupted. Therefore, an exact correlation between the CRC fail rate and the BER is not possible. Under certain assump-
tions an approximation can be made as follows. A direct input and output packet containing 20 bytes results in 160 bits
of data being sent and therefore, a transmission of 63 packets is equivalent to 10,000 bits. A BER of 10
error for every 10000 bits sent or received. Assuming the best case of only 1 bit error in a failed packet, having 1 failed
packet for every 63 received is about equal to a BER of 10
c) UNRETURNED MESSAGES ALARM CH1(2)
PATH: SETTINGS PRODUCT SETUP
UNRETURNED
MESSAGES ALARM CH1
5
The C30 checks integrity of the direct input and output communication ring by counting unreturned messages. In the ring
configuration, all messages originating at a given device should return within a pre-defined period of time. The unreturned
messages alarm function is available for monitoring the integrity of the communication ring by tracking the rate of unre-
turned messages. This function counts all the outgoing messages and a separate counter adds the messages have failed
to return. When the unreturned messages counter reaches the user-definable level specified by the
setting and within the user-defined message count
CH1 THRESHOLD
FlexLogic™ operand is set.
ALM
When the total message counter reaches the user-defined maximum specified by the
setting, both the counters reset and the monitoring process is restarted.
COUNT
The operand shall be configured to drive an output contact, user-programmable LED, or selected communication-based
output. Latching and acknowledging conditions, if required, should be programmed accordingly.
The unreturned messages alarm function is available on a per-channel basis and is active only in the ring configuration.
The total number of unreturned input and output messages is available as the
INPUTS UNRETURNED MSG COUNT CH1
5-56
ACTUAL VALUES
CRC ALARM CH1 MESSAGE COUNT
should be set to 10 × 60 × 1 = 600.
DIRECT I/O
UNRET MSGS ALARM CH1
FUNCTION: Disabled
UNRET MSGS ALARM CH1
MESSAGE
MESSAGE COUNT: 600
UNRET MSGS ALARM CH1
MESSAGE
THRESHOLD: 10
UNRET MSGS ALARM CH1
MESSAGE
EVENTS: Disabled
actual value.
C30 Controller System
STATUS DIRECT INPUTS
to "10000", corresponds a time window of about 160 minutes at
–4
.
UNRETURNED MESSAGES ALARM CH1(2)
Range: Enabled, Disabled
Range: 100 to 10000 in steps of 1
Range: 1 to 1000 in steps of 1
Range: Enabled, Disabled
UNRET MSGS ALARM CH1 COUNT
ACTUAL VALUES
5 SETTINGS
actual
CRC FAIL COUNT CH1
CRC ALARM CH1 MESSAGE COUNT
–4
implies 1 bit
UNRET MSGS ALARM
, the
DIR IO CH1 UNRET
UNRET MSGS ALARM CH1 MESSAGE
STATUS DIRECT
GE Multilin
CRC