Profichip VPC3+C - Global_Control (SAP 58)

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6 PROFIBUS DP Interface

User_Watchdog_Timer

After start-up (DATA-EXCH state), it is possible that the VPC3+C continu-

ally answers Data_Exchange telegrams without the user fetching the re-

ceived Dout-Buffers or making new Din-Buffers available. If the user proc-

essor ‘hangs up' the DP-Master would not receive this information. There-

fore, a User_Watchdog_Timer is implemented in the VPC3+C.

This User_WD_Timer is an internal 16-bit RAM cell that is started from a

user parameterized value R_User_WD_Value and is decremented by the

VPC3+C with each received Data_Exchange telegram. If the timer reaches

the value 0000H, the VPC3+C goes to the WAIT-PRM state and the

DP_SM carries out a LEAVE-MASTER. The user must cyclically set this

timer to its start value. Therefore, ‘Res_User_WD = 1’ must be set in Mode

again loads the User_WD_Timer to the parameterized value

R_User_WD_Value and sets ‘Res_User_WD = 0’ (Mode Register 1). Dur-

ing power-up, the user must also set ‘Res_User_WD = 1’, so that the

User_WD_Timer is set to its parameterized value.

6.2.6 Global_Control (SAP 58)

The VPC3+C processes the Global_Control telegrams like already

described.

The first byte of a valid Global_Control is stored in the R_GC_Command

RAM cell. The second telegram byte (Group_Select) is processed

internally.

The interrupt behavior regarding to the reception of a Global_Control

telegram can be configured via bit 8 of Mode Register 2. The VPC3+C

either generates the New_GC_Control interrupt after each receipt of a

Global_Control telegram (default) or just in case if the Global_Control

differs from the previous one.

The R_GC_Command RAM cell is not initialized by the VPC3+C. Therefore

the cell has to be preset with 00H during power-up. The user can read and

evaluate this cell.

In order to use Sync and Freeze, these functions must be enabled in the

Mode Register 0.

50 Revision 1.03

VPC3+C

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