Rockwell Automation 2711 PanelView 550/900 Profibus Communications User Guide - Manual (Page 43)

PROFIBUS DP Communications 43
Publication 2711-6.3
REAL TIME MODULE
The modules that contain data blocks (input block 0 & output block
0) that are exchanged on each PROFIBUS DP scan between the DP
Master and PanelView terminal.
SLAVE LOCKED / UNLOCKED
When multiple DP Masters try to communicate with a slave, the first
DP Master device to communicate locks out communications for
other masters (Slave Locked). If no masters are communicating with
the slave, the slave is unlocked (Slave Unlocked).
WATCHDOG TIMER
A timer used to detect any loss of communications between the
PanelView terminal and its master.