BECKHOFF BK3xx0 - Manual (Page 38)

Notes on the Documentation
36 Fieldbus Components
DP buffer Default Maximum size
Inputs 128 244
Outputs 128 244
Diagnostic Data 64 64
Configuration data 64 244
The sizes can be adjusted through the PrmData. The length is modified in steps of 8 bytes.
Example:
If it is desired to increase the size of the input data, other sizes must be reduced to compensate.
If we have 20 x 4 channel KL3314 thermocouples, then in compact mapping we find 20 Bus Terminals * 4 channels *
2 bytes per channel = 20 * 4 * 2 = 160 bytes
160 bytes is larger than the 128 byte default figure - settings must therefore be modified.
Set PrmData byte 12 bits 4-7 to 15 dec or 0xF hex, set byte for 37 to 160 (input data) and byte 38 to 96 (output data).