ProSoft Technology MVI56-PDPS - Manual (Page 51)

Diagnostics and Troubleshooting MVI56-PDPS ♦ ControlLogix Platform
Profibus DP Slave Communication Module
ProSoft Technology, Inc. Page 51 of 88
April 22, 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.
Further explanation of Status Register [0]: Word 9 Bit states
Bit 0
Offline/Passive-idle
ƒ
0 = SPC3 exits offline and goes to passive-idle. The idle timer and Wd timer
go offline.
ƒ 1= SPC3 exits offline and goes to passive-idle. The idle timer and Wd timer
are started.
Bit 4, 5
ƒ
10 = Data Exchange State is Normal. The SPC3 has a correct configuration.
Bits 6, 7
ƒ
Watchdog Timer
ƒ Automatic Baud Rate Identification
The SPC3 is able to identify the baud rate automatically. The "baud search" state
is located after each RESET and also after the watchdog (WD) timer has run out
in the "Baud_Control_state." As a rule, SPC3 begins the search for the set rate
with the highest baud rate. If no SD1 telegram, SD2 telegram, or SD3 telegram
was received completely and without errors during the monitoring time, the
search continues with the next lowest baud rate.
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.