Critical Link, LLC PROFIBUS / RS485 Expansion Kit www.CriticalLink.com 5 March 2014 FEATURES PROFIBUS Protocol (SoM Dependent) - Certified by PI International - Electrically Isolated Interface - Up to 6Mbaud operation RS485 Protocol - Electrically Isolated Interface - Up to 115,200 baud rate On-Board termination resistor (2.2 x 1.2 actual size) - Jumper selectable Compatible with MitySOM/MityDSP based Development Kits from Critical Link DESCRIPTION The PROFIBUS/RS485 Expansion Kit is compatible with Critical Links line of MitySOM/MityDSP based development kits one is required to interface with this expansion kit. Specific MitySOM/MityDSP based System on Modules support PROFIBUS. All MitySOM/MityDSP based System on Modules support RS485, see Table 1 for details concerning SoM support for PROFIBUS. Table 1: Critical Link SoM PROFIBUS Support Module Type PROFIBUS Support RS485 Support MitySOM-1810 Yes Yes MitySOM-1810F Yes Yes MityDSP-L138 Yes Yes MityDSP-L138F Yes Yes MitySOM-1808 No Yes MitySOM-1808F No Yes MitySOM-3359 No Yes 1 Copyright 2007-2012, Critical Link LLC Critical Link, LLC PROFIBUS / RS485 Expansion Kit www.CriticalLink.com 5 March 2014 PROFIBUS Interface Description Texas Instruments Inc. (TI) has integrated PROFIBUS functionality into its AM1810 Sitara ARM microprocessor (MPU). The expansion kit utilizes one of the AM1810 onboard UARTS through the Expansion Header on the PROFIBUS DEVELOPMENT KIT base board. This eliminates the need of an external ASIC or FPGA to support the PROFIBUS interface. Customers using a supported SoM in their industrial application can save cost and reduce design complexity as well as PCB space. Furthermore, the industrial application benefits from the low-power architecture of the Sitara ARM MPU and the MitySOM-1810 or MityDSP-L138 platforms from TI and Critical Link. The ARM MPU PROFIBUS Slave solution has been certified by PROFIBUS International (PI). The PROFIBUS real-time frame handler (Fieldbus Data Link or FDL) is encapsulated in the Programmable Real-Time Unit Subsystem (PRUSS), which is part of the Sitara ARM MPU on-chip peripherals. The PRUSS uses one Universal Asynchronous Receiver/Transmitter (UART) and a timer to generate PROFIBUS-compliant frames. The industrial application and the PROFIBUS DP-Protocol (Layer 7) are operated on the ARM. The solution is completed with an RS-485 transceiver suitable for harsh environments, such as TIs ISO1176 which is found on the PROFIBUS-RS485 Expansion Kit board. The PROFIBUS subsystem uses the PRUs that implement real-time frame handling PROFIBUS message transmission, frame validation and communication with the ARM processor. The PROFIBUS subsystem interfaces with one of the UARTs in the Sitara ARM MPU, which is designated for PROFIBUS communication at up to 6Mbaud data rate. The PRU uses interrupts to interact with the ARM where the PROFIBUS stack (Layer 7, DP Protocol) and the industrial application is run. All process data handling like cyclic, acyclic and service access point (SAP) between the PROFIBUS stack on ARM and the PRU is through the internal memory. Linux Driver and API examples are available to support PROFIBUS functionality. Additional details about PROFIBUS support can be found on TIs website (www.ti.com/tool/profibus). RS485 Interface Description When using any of the Critical Link MitySOM/MityDSP based System on Modules (Som) the RS485 protocol is supported. When paired with our MitySOM/MityDSP based development kits the RS485 Expansion Kit can be seamlessly added to your design. A data rate of up to 115,200 baud is supported through this interface. Linux Driver and API examples are available to support RS-485 functionality. 2 Copyright 2007-2012, Critical Link LLC