Watchdog NTC to F500 PGW CAI REV0 July 2014
The Watchdog speed is encoded in the following manner. Four hexadecimal digits are
used to represent the measured speed for the Watchdog. The rightmost three and a half
are the main body of the speed and the upper half of the fourth is the position of the
decimal place within the information. If the most significant two bits are ‘00’ then
decoding of the speed is not required. If the two bits are ‘01’, then the resulting value
should be divided by 10 and if the two bits are ‘10’ then the speed should be divided by
100. The top two bits should never be ‘11’ as this has no meaning.
Description (e.g. most significant bits of the first speed byte 3)
Bits 5-0 of the first byte and the whole second represent the speed.
Same as above but the speed and should be divided by 10
Same as above but the speed and should be divided by 100
An example of this can be seen below.
Watchdog speed = 6E (e.g. byte 3) & 1E (e.g. byte 2). The leftmost digit (6) = ‘0110’ in
binary which can be separated into ‘01’ (bits 7 and 6) for speed scaling and ‘10’ (bits 5
and 4) for the upper speed digit. If you strip off bits 7 and 6 you are left with a decoded
value of 2E & 1E for the speed and ‘01’ or divide by 10 for the scaling. The speed 2E1E
converted to decimal = 11806 and then divided by 10 results in an actual speed of 1180.6.
By default the Watchdog will display speed in pulses per minute but it can be scaled to
display any value required, refer to the Watchdog manual for further detail.
The Watchdog status is encoded as described in the following manner.
Two data bytes are used to represent the status for the Watchdog. The first status byte
(e.g. byte 5) is the status code and the second byte (e.g. byte 4) represents any data which
is associated with the status code. All data is in hexadecimal.
Watchdog is calibrating (% complete).
Elevator is stopped due to persistent belt slip.
Elevator is stopped due to persistent over calibration.
Misalignment detected on Top & Bottom sensors.
Elevator is stopped and is ready to run (Normal stop
condition)
Elevator is accelerating. (xx seconds remain)
Elevator running within programmed limits.
Stop relay has been de-energised (Fault stop
condition)
Misalignment detected. (xx seconds to alarm)
Over speeding: Alarm relay about to de-energise (xx
seconds to alarm)
Misalignment detected at the top of the elevator.
Over speeding: Stop relay about to de-energise (xx
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