Providing absolute machine encoder position over a standardized protocol

Note: Absolute encoder protocol is ignored in TyphoonSim. Changing its value will not affect TyphoonSim simulation at all.

Real-time only: This document is valid only for real-time simulation.

Overview

Note: Absolute encoder protocol support is dependent on your firmware configuration. Please refer to the Device Configuration Table for more information.

Absolute encoders are capable of providing a unique machine rotor position and a number of machine rotor revolutions. The output of a singleturn absolute encoder indicates the current shaft position, making it an angle transducer. The output of a multiturn absolute encoder indicates the current number of machine rotor revolutions.

Machines running on a HIL device can send encoder data to external devices using EnDat, BiSS, or SSI standardized protocols.

Singleturn absolute encoder resolution is defined by the Encoder ppr property on the Feedback tab of the selected machine's component properties dialog. In order to transmit complete machine rotor position information via chosen absolute encoder protocol, the following condition should be satisfied:

Encoder ppr = 2_{}^{n}

where n is the number of singleturn bits. If the assigned Encoder ppr value is greater than 2ⁿ, information about the machine rotor position sent through the singleturn encoder will be incomplete and will result in an error. If the Encoder ppr value is less than 2ⁿ, a certain number of the MSBs of the singleturn absolute encoder will be zeroed.

If the Enable multiturn property is checked, you can specify a number of multiturn bits for providing information about the current number of machine rotor revolutions. When one full revolution of the machine rotor is made, the multiturn counter will be increased.

Figure 1. Example of proper machine absolute encoder protocol settings in real-time perspective

Note: Maximum number of singleturn or multiturn absolute encoder bits specified on the machine's component mask is limited to 30.

Note: Multiturn absolute encoder support is available from the 2024.3 Typhoon HIL software version.

Protocol limitations

Implemented protocol limitations are:

General:
- Binary encoding only, Gray code is not supported
- Inter-frame recovery time: the HIL requires a minimum idle time of 20 µs between consecutive frames
EnDat:
- Only the Encoder send position values command is supported (code 000111). This EnDat 2.1 command is compatible with EnDat2.2
- Position values are sampled with interrupted clock
- CRC field is not computed; provided as 0 in the frame
- Position data is transmitted LSB first, as defined by the protocol
BiSS (implementing a simplified BiSS-C protocol):
- Only point-to-point configuration is supported
- Only Single Cycle Data (SCD) is supported
- CDS bit is set to 0, indicating Single Cycle Data (SCD) frame
- Position data is right-aligned, as defined by the protocol
- CRC field is not computed and not provided in the frame
- No Error or Warning status bits, nE and nW are not provided in the frame
- No register access, BiSS register read/write cycles are not implemented
SSI:
- Only point-to-point configuration is supported
- Position data is left-aligned, as defined by the protocol

Note: The HIL device accepts clock frequencies up to the protocol specification maximum (SSI: 2 MHz, BiSS-C: 10 MHz, EnDat 2.2: 16 MHz). The HIL hardware imposes no additional clock frequency restriction beyond the protocol standard.

Note: BiSS-C leaves the DATA field layout implementation-specific. The external device should be configured to match the HIL output: binary encoding, right-aligned position data, no CRC, no nE/nW bits, and the bit counts set in the machine component dialog.

Digital input configuration

Clock and data signals from an external device should be connected to the desired digital input pin on the HIL device. These pins need to be defined in the machine dialog window. On the Feedback tab, values for clock and data pins need to be defined. The connected signal can be active high, or active low, depending on the connected external device.

Note: The Data DI pin and its corresponding DI logic can be specified only if EnDat is chosen as the machine absolute encoder protocol.

Digital output configuration

Data from the HIL device (machine_name.EnDat data, machine_name.EnDat gate, machine_name.BiSS data and machine_name.SSI data) can be set to any digital output. Digital outputs are defined in the Digital Outputs window in HIL SCADA (Figure 2).