The document discusses the importance of customized System-on-Chip (SoC) solutions for industrial automation, highlighting the limitations of traditional ARM-based chipsets tailored for consumer electronics. It emphasizes the benefits of integrating programmable real-time units (PRUs) within SoCs, such as the Texas Instruments AM335x and AM43xx families, to enhance real-time processing and scalability for industrial applications. The PRU-ICSS subsystem allows for the implementation of complex industrial automation protocols, addressing connectivity and performance challenges inherent in existing designs.

1. Customized SoC for Industrial Automation Markets
Introduction
Industrial Automation is an important market segment which deals with semi or complete
automation of the industrial manufacturing machinery and associated tools. Microcontrollers have
been playing an important role in Industrial Automation markets for performing automated tasks.
For high-end process automation, the usage of customized or highly specific Programmable Logic
Controllers and x-86 or Power-PC based Single Board Computers is common. Traditional ARM based
Chipsets and System-on-Chip products have focused exclusively on Consumer Electronics and
related fields. However, there is a compelling reason for having customized ARM based Chipsets
which can cater to market verticals like Industrial Automation, Portable Instrumentation, Portable
Medical and Point-of-Sale.
In these market segments, the traditional approach has been to utilize a general purpose ARM
chipset which is then interfaced with custom ASIC to achieve the intended functionality for an
Industrial Automation or Retail Point of Sale kind of End-Product. This approach not only increases
the BOM cost, but limits the scalability of the product for future generations and OEM/ODMs end up
spending significant amount of their R&D efforts in building new products for these markets.
For example, let us consider the most common required interfaces for an Industrial Automation
product i.e., ADC and CAN Interfaces. In traditional approaches, we would typically have the below
mentioned configuration.
Figure 1: Block Diagram of Custom AFE Interface in Legacy Designs
Depending on the logic implemented inside the custom ASIC/FPGA, the Analog Front End may be a
separate/discrete IC or maybe implemented inside the custom ASIC itself.
The above approach for designing products for Industrial Automation does not scale well and causes
huge turn-around time for the Device Manufacturers whenever they are planning/thinking of
introducing new products into the market.
This becomes even more challenging when we would like to interface other industrial interfaces
such as ProfiBus, EtherCAT and CAN.
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Processor Custom ASIC/
FPGA
Analog Front End
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2. CUSTOMIZED SOC FOR INDUSTRIAL AUTOMATION MARKETS
Solution
In order to address the scalability and the lesser turn-around time for product development on the
Industrial automation domain, it is better to go with a customized Silicon /System-on-Chip
(SoC)which not only supports the low-power ARM processor with good amount of Level 1 and Level
2 Cache, but which also has custom interfaces such as CAN, ADC, PWM, SPI interfaces added as on-
chip peripherals.
The Texas Instruments AM335x and AM43xx family of processors offers a unique combination of
cost effective chip solution consisting of Connectivity Options, High Integration of Peripherals,
support for Graphical interface and scalable features.
The AM335x and the latest AM43xx processor family is an ideal chipset for implementing end
products for market verticals such as Barcode Scanners, Home Gateway/Industrial Gateway
Controllers, Portable Data Terminals, Point of Service Devices and Industrial Control/Automation
Devices.
The AM43xx is a cost effective solution since it addresses the important connectivity related issue
that we discussed in the introduction of this whitepaper. The AM335x provides BOM Cost
optimization since it internally encapsulates interfaces such as the ADC, PWM, CAN, SPI, Ethernet
and 3D Graphics.
Another major attraction of the AM43xx family is the addition of the Programmable Real-Time Unit
Modules. The Programmable Real-Time Unit Subsystem and Industrial Communication SubSystem
(PRU-ICSS) consists of dual 32-bit RISC cores (Programmable Real-Time Units, or PRUs), data and
instruction memories, internal peripheral modules, and an interrupt controller (INTC). When we say
programmable, it means that these RISC Cores can be loaded with any user defined
program/application, along with their access to pins, events and all SoC resources, providing
flexibility in implementing fast real-time responses, specialized data handling operations, custom
peripheral interfaces, and in offloading tasks from the other processor cores of the SoC.
The PRU-ICSS hardware can be used for:
• Industrial Automation related Applications using the ICSS Block
• Broad market/Consumer related Applications using just the PRU block
Motivation for PRU
In this section, we will explore the motivation and the need to integrate a peripheral like the PRU
within the System-On-Chip and later examine one specific use-case of the PRU i.e., Communication
Sub-system for Industrial Automation.
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3. CUSTOMIZED SOC FOR INDUSTRIAL AUTOMATION MARKETS
For real-time applications such as Programmable Logic Controllers, Control Machinery, the
requirement to respond to real-time events is a critical one. If we take any modern System-On-Chip,
they typically consist of atleast two levels of Interconnect/bus and also multiple levels of
cache/internal/external memory which makes it difficult to respond to real-time events within tens
of nanoseconds.
So this introduces a kind of designer’s dilemma that while modern System-On-Chip offersthe best
connectivity/interfaces, cache and power requirements, at the same time cannot handle real-time
events/processing withintens of nanoseconds. To overcome such performance issues, there has
been one design argument that we need to integrate or merge Special Real-time Co-processors
along with the regular ARM chipsets. This is analogous to integration of special purpose Audio/Video
Co-processors to off-load the Audio/Video processing logic to custom real-time cores.
Another associated design challenge is that adding a real-time co-processor may not solve the real-
time performance issue altogether. The real-time co-processor should also have necessary
interfaces/operational infrastructure to be able to detect real-time events being triggered from the
external world and they should be able to detect the occurrence of the real-time event within a few
nanoseconds.
This leads us to the second design conclusion that these Real-time Co-processors should also have
their own interrupt Infrastructure and access to the external world via some kind of I/O Pins or serial
interfaces. Typically providing access to at least some of the peripherals would also make the real-
time coprocessor much more flexible in terms of integration and general usage.
To summarize, the Real-time Coprocessor should meet/address the following requirements:
1. Have its own instruction execution unit independent of the ARM core
2. Should not utilize instruction pipeline cycles which will not guarantee real-time execution
3. Should have its own interrupt controller/mechanism to be able to detect real-time external
events
4. Should have a separate instruction and data memory to ensure that the instruction fetch
and data fetch are not multiplexed on the same lines
5. Should also have access to the external world via some General Purpose Pins or peripherals
6. Should preferablyshare the interconnect/external bus with the main ARM Core such that the
real-time co-processor can also configure/control the memory mapped peripherals such as
UART, PWM, SPI etc.
Texas Instrument’s SITARA family of processors provides the above mentioned real-time coprocessor
integration [different processors have different level of PRU integration] and can be utilized for most
industrial automation, control machinery applications. The below block diagram provides a high-
level view of how the real-time coprocessor or the PRU has been integrated into the System-on-
Chip.
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4. CUSTOMIZED SOC FOR INDUSTRIAL AUTOMATION MARKETS
Figure 2: ARM and PRU Sub-system Block Diagram in AM43xx SoC
As shown in the above block diagram, the Programmable Real-Time Unit [PRU] has been integrated
into the Interconnect bus of the main ARM core, it has its own set of Interrupt Controller,
Instructionand Data Memory and access to peripherals. This provides the best integration for real-
time co-processors to handle various product/application requirements. In the next section, we will
examine one specific use-case for the PRU i.e., Communication for Industrial Automation and explain
how the PRU helps in implementing one-such use-case.
Connectivity Requirements for Industrial Automation
Industrial Automation products usually perform automation/control/configuration of manufacturing
and material assembly/handling devices. Programmable Logic Controllers [PLC] are a standard form
of implementing the General Control/Configuration of the Industrial Machinery and devices.
In order to automate big/large mechanical machines and setup, it is important to have them covered
with electronic linkages. It is not feasible to go for a Point-to-Point coverage/linkage between the
machines due to the setup cost and cost involved in a potential failure of the system. Hence a bus
based approach of electrical wiring interconnecting mechanical machines, programmable logic
controllers, assembly devices and centralized operations control centers makes more sense.
Once the bus architecture is in place, we can designate each individual device/machine as a node on
the bus. These nodes can talk to a centralized control center which in turn communicates to the rest
of the nodes present on the bus. Thus, we end up having a Master Node/Slave Nodes kind of
concept.
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5. CUSTOMIZED SOC FOR INDUSTRIAL AUTOMATION MARKETS
The Software Protocols used to exchanges messages among the various nodes needs to employ an
Initiator/Responder kind of roles during the message exchange period. This also leads to the concept
of Master/Slave Nodes utilized inside the Protocols working on the Industrial Devices.
For example, EtherCAT Protocol encapsulates its messages inside a standard Ethernet Frame and
uses the concept of Master and Slave Nodes to exchange data between various devices/assembly
machines connected in an Industrial factory setup.
Conclusion
The AM335x and the recent AM43xx is an ideal fit for the implementation of such Industrial
Automation devices by exploiting the PRU-ICSS Sub-system. Various Industrial Automation protocols
such as ProfiBus, ProfiNet, Ethernet/IP, EtherCAT can be implemented and loaded into the PRU
Hardware Core. The PRU Module of AM43xx family of processors contains better instruction sets
and additional interfaces to support working of complex Industrial Automation Protocols inside the
PRU-ICSS engine.
Author
Ravindra BS is working as a Technical Manager in Mistral Solutions and has over 15 years of
experience in the embedded domain specializing in Windows Embedded and Linux. He has worked
on the TI OMAP5910, OMAP35x and OMAP4 related Products for various customers of Texas
Instruments. Ravindra holds an engineering degree in Computer Science from Bangalore University.
References
1. SPRU264.pdf – “Ensuring Real-time Predictability” Whitepaper from Texas Instruments
Authors Melissa Watkins and Carlos Betancourt.
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This document and the data disclosed herein is proprietary and is not the be reproduced, used
or disclosed in whole or in part to anyone without written authorization of Mistral.

6. CUSTOMIZED SOC FOR INDUSTRIAL AUTOMATION MARKETS
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