DESCRIPTION
The TMC8100 includes a programmable microcontroller optimized for serial synchronous and asynchronous absolute encoder protocols up to 16Mbit/s. It can replace dedicated encoder protocol interface ICs and FPGA implementations while supporting in-system updates for different encoder capabilities or for switching to other encoder protocols. The TMC8100 is a compact, cost-effective, and flexible communication solution for adding absolute encoder support to industrial drives.
This application note provides details on the TMC8100 software reference implementation supporting Tamagawa absolute encoder.
FEATURES
- Tamagawa T-Format Implementation
- Supports 2.5Mbps Absolute Encoder
- Supports Data Readout and On-the-Fly Cyclic Redundancy Check/CRC Checksum Calculation
APPLICATIONS
- Servo Drive Position Feedback
- Servo Drive Motor Control
SYSTEM DESCRIPTION
Servo motor drives, e.g., in industrial applications typically require accurate, reliable, and low-latency position feedback. For a long time, optical encoders with incremental A/B/N output have been the industry standard. Nevertheless, absolute position encoders are gaining traction often with additional functionality and different interface protocols (mostly vendor-specific). An example is the T-Format protocol from Tamagawa for serial transfer of digital data between encoder and controller. The physical layer is based on the RS485 standard and capable of transmitting position values, diagnostic information, and allows reading and writing of the internal memory of the encoder.
The encoder with T-Format protocol connects to the TMC8100-EVAL-KIT through a single-shielded four-wire cable (Figure 1). The four wires are as follows:
- +5V and GND: encoder power supply and ground connection
- DATA+ and DATA-: differential RS485 signals for data communication (bidirectional)
The reference implementation features:
- 2.5Mbps data rate as supported by the T-Format protocol
- Send command (ID0, ID1, ID2, ID3, ID6, ID7, ID8, IDC, IDD) and receive reply
- Packing and unpacking of data
- On-the-fly calculation of CRC checksum and adding to transmit data
- On-the-fly calculation of CRC checksum and compare with received CRC
The reference implementation is available as source code. Users may use this as a starting point and apply changes as required by the application.
