ProSoft Technology 5205-DFNT-PDPS - Manual (Page 46)

PDPS ♦ ProLinx Gateway Diagnostics and Troubleshooting
PROFIBUS DP Slave
Page 46 of 61 ProSoft Technology, Inc.
December 31, 2008
After identifying the correct baud rate, SPC3 switches to the "Baud_Control"
state and monitors the baud rate. The monitoring time can be parameterized
(WD_Baud_Control_Val). The watchdog works with a clock of 100 Hz (10
milliseconds). The watchdog resets each telegram received with no errors to its
own station address. If the timer runs out, SPC3 again switches to the baud
search state.
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).