AN 999: Drive-on-Chip with Functional Safety Design Example: Agilex™ 7 Devices

ID 823627
Date 7/04/2024
Public

Visible to Intel only — GUID: hrs1716294401440

Ixiasoft

Document Table of Contents

4.3.1.1. Safety Function Block

Contains the FUSA and timer heartbeat generator, speed estimator, and payload generator.

FUSA and Timer Heartbeat Generator

The heartbeat generator monitors the condition of all the other IPs in the FPGA and HPS channels. The generate bit is a control signal that toggles the heartbeat.

For the FPGA, the generate input is derived from the FPGA Comparison Function state machine's start output, which in turn triggers from the timeout. Therefore, the FPGA heartbeat signal indicates correct restarting controlled by the software and operating comparison function state machine.

Speed Estimator

The speed estimator estimates the speeds of the motor model based off quadrature encoder pulse count. Using this calculated value, the module determines respective safety bits, which pass into the external safety logic. The main algorithm of the estimator is similar to the one in drive on chip, with additional safety diagnostics. The speed estimator module controls local parameters and modifies sampling frequencies.

Payload Generator

The payload generator takes in many different signals from around the overall safety block and generates a payload with all the relevant information. The FPGA-side payload is passed into the cross-comparison block for relevant and respective checks.

Table 2.  Payload Generator Format DefinitionThe table shows the format for the payload data.
Bit range Length Data Description
[0] 1 bit Overspeed indication 1 for Overspeed
[25 : 1] 25 bits Estimated speed Measured in rpm
[31 : 26] 6 bits Sequence Implemented an internal counter to register the sequence of measurements. (0-128) always looping around