Object 3496h: Fieldbus synchronization parameters
This set of objects is used to set or read parameters for the fieldbus synchronization used in the interpolated position mode (7) and the cyclic-modes 8 etc. The synchronization between a fieldbus master and the AKD is similar in all the supported fieldbus systems.
The AKD internal 16[kHz] interrupt function is responsible for calling the PLL function. This PLL function is called once per fieldbus cycle (set by object 60C2 sub 1 and 2). If the fieldbus sample period is for example 1[ms], the PLL code is called every 16th time of the 16[kHz] IRQ of the AKD.
Once in a fieldbus sample the SYNC-telegram must arrive, which resets a PLL counter in the Drive. After some time the already mentioned PLL function is called and reads back the time from that PLL counter.
Depending on the measured time the PLL function extends (in case that the measured time is too low) or lowers (in case that the measured time is too high) the sample time of the upcoming 16[kHz] tasks for one fieldbus sample by a selectable value (object 3496 sub 4) in order to move the PLL function closer to the expected distance (object 3496 sub 1).
Beside the objects mentioned here the parameter FBUS.SAMPLEPERIOD is important, which is set by object 60C2 sub 1 and 2. This setting is required in order to share the fieldbus sample time with the slave. This information is e.g., needed for being able to call the AKD internal PLL function once per fieldbus sample.
|
Index |
|
|
Name |
FBUS synchronization parameters |
|
Object code |
Array |
|
Data type |
UNSIGNED32 |
|
Category |
optional |
|
Subindex |
0 |
|
Description |
highest sub-index supported |
|
Category |
mandatory |
|
Access |
R/O |
|
PDO mapping |
not possible |
|
Value range |
0x4 |
|
Default value |
0x4 |
|
Subindex |
1 |
|
Description |
FBUS.SYNCDIST |
|
Category |
optional |
|
Access |
R/W |
|
PDO mapping |
not possible |
|
Value range |
UNSIGNED32 |
|
Default value |
320000 [ns] |
Sub 1 is the expected time distance in nano seconds between clearing the PLL counter and calling the PLL function.
|
Subindex |
2 |
|
Description |
FBUS.SYNCACT |
|
Category |
optional |
|
Access |
R/W |
|
PDO mapping |
not possible |
|
Value range |
UNSIGNED32 |
|
Default value |
320000 [ns] |
Sub 2 is the actual time distance in nano seconds between clearing the PLL counter and calling the PLL function.
|
Subindex |
3 |
|
Description |
FBUS.SYNCWND |
|
Category |
optional |
|
Access |
R/W |
|
PDO mapping |
not possible |
|
Value range |
UNSIGNED32 |
|
Default value |
70000 [ns] |
Sub 3 is a window, which is used in order to consider the drive as being synchronized. The AKD is considered as synchronized in the following case:
FBUS.SYNCDIST – FBUS.SYNCWND < FBUS.SYNCACT < FBUS.SYNCDIST + FBUS.SYNCWND
|
Subindex |
4 |
|
Description |
FBUS.COMPTIME |
|
Category |
optional |
|
Access |
R/W |
|
PDO mapping |
not possible |
|
Value range |
UNSIGNED32 |
|
Default value |
150 [ns] |
Sub 4 value indicates the time, which is used for extending or lowering the sample rate of the AKD internal 16[kHz] IRQ, which is responsible for calling the PLL function. The default sample time is 32 * 1/16[kHz] = 2[ms].
The sample time of the AKD high prior interrupt is determined by
62.5[µs] – FBUS.COMPTIME if FBUS.SYNCACT > FBUS.SYNCDIST.
The sample time of the AKD high prior interrupt is determined by
62.5[µs] + FBUS.COMPTIME if FBUS.SYNCACT < FBUS.SYNCDIST.
