Emerson E300 Series Design Manual page 236

Safety Product Mechanical
information information installation
See Drive Encoder Low Speed Update Rate Active (C27) for more details.
Drive Encoder Type (C01): Any other type of device Drive Encoder Calculation Time (C24) has no effect.
C25 Drive Encoder Recovery Time
Mode RFC-A, RFC-S
Minimum 5
Default 30
Type 8 Bit User Save
Display Format Standard
Coding RW
Drive Encoder Type (C01): EnDat, SSI, BiSS
Drive Encoder Recovery Time (C25) is the time that must be allowed after each message interchange before a new message begins.
Drive Encoder Type (C01): Any other type of device
Drive Encoder Recovery Time (C25) has no effect.
C26 Drive Encoder Line Delay Time
Mode RFC-A, RFC-S
Minimum 0
Default 5
Type 16 Bit User Save
Display Format Standard
Coding RO, ND, NC, PT
Drive Encoder Type (C.01): EnDat, SC EnDat, BiSS
During position feedback initialization the transmission delay between the position feedback interface and the encoder and back again is measured
and stored in Drive Encoder Line Delay Time (C26). This value is then used to compensate for this delay so that the clock/data skew does not prevent
the data from the encoder from being read. This means that longer line lengths can be used with these feedback devices provided the correct cable
and connection arrangements are used.
Drive Encoder Type (C01): Any other type of device
Drive Encoder Line Delay Time (C26) is always zero.
C27 Drive Encoder Low Speed Update Rate Active
Mode RFC-A, RFC-S
Minimum 0
Default
Type 1 Bit Volatile
Display Format Standard
Coding RO, ND, NC, PT
Drive Encoder Type (C01): EnDat, SSI, BISS
There is a delay when the position information is obtained via a communications interface from an encoder. It is assumed that the position information
is taken from all types of encoder at a fixed datum point during each sample period. The drive initiates the comms transfer at a suitable point in
advance of the datum to ensure that the position information is available when required. A correction is then applied to the position information based
on the change of position over the previous sample and the advance time so that the position appears to have been sampled at the datum. If the
communications exchange, including allowing the encoder a recovery time (Drive Encoder Recovery Time (C25)), is completed in 60 μs and the time
required to obtain the full position is completed in 40 μs then the position is sampled at each current controller task and Drive Encoder Low Speed
Update Rate Active (C27) = 0. Otherwise if the communication exchange is completed in 230 μs the position is sampled every 250 μs and Drive
Encoder Low Speed Update Rate Active (C27) = 1. If the complete exchange takes any longer a trip is initiated. The following table shows the
calculations used by the drive to determine the necessary time to obtain the required data.
236
Electrical Getting
User Menu A Commissioning
installation started
Advanced
Diagnostics Optimization CT MODBUS RTU Technical Data
Parameters
Maximum 100
μs
Units
Update Rate Background read, auto-configuration write
Decimal Places 0
Maximum 5000
Units ns
Update Rate Background read, auto-configuration write
Decimal Places 0
Maximum 1
Units
Update Rate Background write
Decimal Places 0
E300 Design Guide
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