Pro-face GP77R Series Connection Manual page 9

Hitachi Industrial Equipment System - Ethernet
PLC Device Block Write Restrictions
The GP unit processes data internally by separating data into blocks of 1024 words.
Therefore, when a Block Write is requested that uses 41 or more words and will
exceed the 1024 word limit, the following features cannot be used.
- PLC Device Write using D-Script's Memory Operation Feature
- Write from GP/GLC SRAM to PLC Device using Filing Feature
- Write to LS Area's Read Area
When using these settings, a Host Communication Error may occur.
If an error occurs, separate the data so that the number of words used by the Block
Write is 1024 or less.
GP-PRO/PBIII for Windows Device/PLC Connection Manual
8