Cyclic Data; What Is Cyclic Data; Data Formats - Leroy-Somer digitax st User Manual

7

Cyclic data

7.1

What is cyclic data?

Cyclic data transfer is a method of transferring data on a regular time period, often
known as 'polled data'. High-speed data transfer is achieved by transmitting only data
bytes over the PROFIBUS-DP network and using local mapping information within the
SM-PROFIBUS DP-V1 and PROFIBUS-DP master controller to ensure that the correct
data is sent to the correct locations. The flexibility of the SM-PROFIBUS DP-V1 means
that each cyclic data OUT channel can be directed to any read/write drive parameter.
Similarly each cyclic data IN channel can use any drive parameter as a source of data.
• The term OUT data refers to data that is transmitted out of the master to the
NOTE
slave.
• The term IN data refers to data that is returned from a slave into the master.
• Cyclic data mapping cannot be changed dynamically, as changes to the
configuration (mapping parameters, etc.) will only take effect during
initialisation of the SM-PROFIBUS DP-V1.
• The maximum number of 16-bit mappings that is possible is: 32 with only
cyclic data, 31 with CT Single Word (Mode 1) non-cyclic data and 28 with
PPO4 Word (Mode 2). This requires data compression to be enabled, see
section 12.5 Cyclic data compression for more information.
• The maximum number of 32-bit mappings that is possible is: 16 with only
cyclic data, 15 with CT Single Word (Mode 1) non-cyclic data and 14 with
PPO4 Word (Mode 2).
See section 12.5 Cyclic data compression for information on using data compression
with 16-bit parameters.
7.2

Data formats

The SM-PROFIBUS DP-V1 can be configured with up to sixteen 32-bit or thirty-two 16-
bit cyclic IN and OUT data words. IN and OUT cyclic data words are mapped using ten
mapping (pointer) parameters, one for each mapping.
To utilize the full range of thirty-two cyclic IN and OUT data words the 'block mapping'
mode must be used (see section 12.6 Block mapping ).
By default all drive parameters are cast as 32-bit (two 16-bit words) therefore thirty-two
NOTE
cyclic words gives sixteen possible drive parameters. Data compression reduces the
number of cyclic words required for drive parameters of 16-bit (or less) to 16-bits thus
allowing for thirty-two possible 16-bit parameters. Any 32-bit parameters mapped will
still require two 16-bit words even with compression turned on.
In addition to cyclic data, non-cyclic data (see section 8.1 What is non-cyclic data? )
exchange is also possible by the following methods:
• DP-V1 parameter access mode.
• Mode 1 - CT single word mode
• Mode 2 - PPO 4 Word mode.
24
www.leroy-somer.com
SM-PROFIBUS DP-V1 User Guide
Issue : a