Operation modes of the EL2521-xxxx

The terminals basically work as follows:

• Basic function
• Frequency setting, also: frequency modulation (setting: driving frequency)
  (the number of pulses to be output is then usually monitored by the higher-level controller)
• or travel distance control (default: max. driving frequency, target position)
  (the terminal automatically moves to a target position and continuously calculates the necessary output frequency)
• Output mode selection
• Frequency modulation or
• Pulse-direction control or
• Incremental encoder

EtherCAT devices are parameterized via PDO (real-time process data) and CoE (acyclic parameters).

For new projects the "enhanced operation mode" 16 or 32-bit is the correct PDO choice.
The enhanced operation mode 16/32-bit was created by the further development of the EL2521. Older EL2521 devices do not support this enhanced operation mode (see following table)! A terminal prior to Firmware 03 / Hardware 02 will not support configuration in enhanced operation mode, since the corresponding objects cannot be controlled.

Compatibility in the case of service An EL2521 employed and projected in enhanced operation mode cannot be replaced by an EL2521 with an older hardware version (<03)!

Process data monitoring It is recommended to monitor the proper behavior of the terminal via the controller using the diagnostic values: WcState: should be 0, if ≠ 0, then this EtherCAT device does not participate in the process data traffic State: if ≠ 8, then the EtherCAT device is not in OP (Operational) state TxPDO State, SyncError: if ≠ 0, then there is no valid process data, e.g. due to wire breakage TxPDO Toggle: if this bit toggles, a new set of process data is available

Delivery state: frequency modulation

The delivery state of the EL2521 is the operation mode frequency modulation with a base frequency of 50 kHz and 15-bit resolution.

For testing in the delivery state, PDO setting Standard 16-bit, the output frequency can simply be set to a value >0, then the EL2521-xxxx starts outputting signals.

The number of pulses output is read back into a 16-bit register. The counter overflows with a message to the controller; this is indicated by the status word SW.3 or index 0x6020:05, overflow or SW.2 or index 0x6020:04 (underflow). In parallel to these two bits, SW.6 or index 0x6010:07 is set as a general error bit. This makes the extension to more than 16-bit easier for the controller software to handle. Furthermore, the overflow can be read from the diagnostic object 0xA000:01 (internal 32-bit extension).

The counter can be cleared by bit 5 in the control word (CW.5). The counter is cleared in the delivery state with a rising edge (feature bit set in index 0x8000:05); this function is level-controlled if the feature bit in index 0x8000:05 = 0. If the feature bit in index 0x8000:0B = 1, then the counter is set to a value specified in index 0x8800:01 by bit 5 in the control word (CW.5).

The PDO "Go counter" in the ControlWord and "Target counter value", although always visible in the process image, can only be used with activated travel distance control.

Relative data

The output frequency depends on the base frequency set in the objects 0x8001:02 or 0x8010:12  to  0x8001:03 or 0x8010:13  and the process data (see table).

Example:

Output frequency = base frequency x process data / 32767
highest resolution = 125 mHz

Base frequency = 100,000 Hz (maximum selected output frequency)
Process data = 0x00FF (255_dec)
Output frequency = 778.22 Hz

Direct data

There is a possibility to directly input the frequency (object 0x8000:08 or 0x8010:08). Here, the process data are multiplied by the factor from object 0x8001:06 or 0x8010:16 and written directly to the synthesis chip.

Example:

Output frequency = frequency factor x process data x 10 mHz
highest resolution = 10 mHz

Frequency factor = 100
process data = 0x00FF (255_dec)
output frequency = 255 Hz

Ramp function

An internal ramp function increases/lowers the current frequency to the preset maximum frequency with the preset parameters in index 0x8800:02 “Maximum frequency” it is activated by index 0x8000:06 or 0x8010:06 “Ramp function active”.

CoE parameters The parameters are to be used depending on operation mode: "normal" from the objects 0x8000, 0x8001, 0x8800 or "enhanced", from the object 0x8010.

The base frequency of the ramp can be selected by index 0x8000:07 or 0x8010:07 “Ramp base frequency”. Bit 1 of the status word (SW.1) or index 0x6010:02 “Ramp active” is set when a ramp is traversed.

The deactivation of this function, which can also take place during operation via CW.1  or index 0x7010:02 “Disable ramp”, results in the enabling of CW.0 or index 0x7010:01 “Frequency select”. This allows the user to quickly change the base frequency during operation.
If CW.0 or index 0x7010:01 = 1 (confirmation by SW.0 or index 0x6010:01), then base frequency 2 in object 0x8001:03 or 0x8010:13 is used instead of base frequency 1 in object 0x8001:02 or 0x8010:12 (CW.0 or index 0x7010:01 = 0).
The input signals T and Z are transferred by the terminal directly to the controller in the status word (SW.4 / SW.5) or index 0x6010:05 / 0x6010:06. The signals are not given any internal pre-processing.

The terminal offers a facility for soft starting and stopping. Using index 0x8001:04 or 0x8010:14 “Ramp time constant rising” the ramp gradient for starting can be set with an accuracy of 10 or 1000 Hz/sec (index 0x8000:07 or 0x8010:07). Index 0x8001:05  or 0x8010:15 “Ramp time constant falling” has the same function for stopping. The process data can be modified during transit of the ramp (CW.2 or index 0x7010:03 “Go counter”), and the terminal then takes the new value as its target frequency.

Resolution

The base frequencies are specified with a resolution of 1 Hz per bit (base frequency 1: index 0x8001:02 or 0x8010:12  or base frequency 2: index 0x8001:03 or 0x8010:13).

The terminal operates internally at 16 MHz with a resolution of 32 bits. This corresponds to a theoretical minimum step size of 0.0037 Hz/step over the entire frequency range. The output stage allows a maximum frequency of 500 kHz to be output.