ProSoft Technology MVI56-PDPS - Manual (Page 66)

MVI56-PDPS ♦ ControlLogix Platform Reference
Profibus DP Slave Communication Module
Page 66 of 88 ProSoft Technology, Inc.
April 22, 2008
Baud Rate Monitoring: The located baud rate is constantly monitored in
'Baud_Control.' The watchdog is reset for each error-free telegram to its own
station address. The monitoring time results from multiplying both
'WD_Baud_Control_Val' (user sets the parameters) by the time base (10 ms). If
the monitoring time runs out, WD_SM again goes to 'Baud_Search'. If the user
carries out the DP protocol (DP_Mode = 1, see Mode register 0) with SPC3, the
watchdog is used for the "DP_Control' state, after a 'Set_Param telegram' was
received with an enabled response time monitoring 'WD_On = 1.' The watchdog
timer remains in the baud rate monitoring state when there is a switched off
'WD_On = 0' master monitoring. The PROFIBUS DP state machine is also not
reset when the timer runs out. That is, the slave remains in the DATA_Exchange
state, for example.
Response Time Monitoring: The 'DP_Control' state serves response time
monitoring of the DP master (Master_Add). The set monitoring times results from
multiplying both watchdog factors and multiplying the result with the momentarily
valid time base (1 ms or 10 ms):
ƒ
TWD = (1 ms or 10 ms) * WD_Fact_1 * WD_Fact_2 (See byte 7 of the
parameter setting telegram.)
The user can load the two watchdog factors (WD_Fact_1, and WD_Fact_2) and
the time base that represents a measurement for the monitoring time via the
'Set_Param telegram' with any value between 1 and 255.
EXCEPTION: The WD_Fact_1=WD_Fact_2=1 setting is not permissible. The
circuit does not check this setting.
Monitoring times between 2 ms and 650 s - independent of the baud rate - can
be implemented with the permissible watchdog factors. If the monitoring time
runs out, the SPC3 goes again to 'Baud_Control,' and the SPC3 generates the
'WD_DP_Control_Timeout-Interrupt'. In addition, the DP_State machine is reset,
that is, generates the reset states of the buffer management.
If another master accepts SPC3, then there is either a switch to 'Baud_Control"
(WD_On = 0), or there is a delay in 'DP_Control' (WD_On = 1), depending on the
enabled response time monitoring (WD_On = 0).
PROFIBUS Status Register [1]: Word 210
SPC3 ASIC slave status information provided to the master.
Baud rate: Bits
0 to 3
The baud rates SPC3 found