APPLICATION NOTE Daisy Chaining of Atmel ATA6836C/ATA6838C ATA6836C/ATA6838C Scope This application note describes the daisy-chaining procedure using Atmel® ATA6836C and ATA6838C. Daisy-chaining Procedure Using Atmel ATA6836C Daisy chaining is a common method to connect several SPI slaves to a single microcontroller SPI port. A single microcontroller SPI port can be shared by utilizing daisy chaining. All Atmel intelligent load drivers with SPI interface support this method. The Atmel ATA6836C/ATA6838C’s daisy-chaining behavior, however, differs from the standard daisychaining procedure. In this application note the ATA6836C represents the two Atmel driver devices ATA6836C and ATA6838C. The daisy-chain arrangement requires only one of each SPI line: Chip select (CS), data in (DI), data out (DO) and clock (CLK), see Figure 1 on page 2. The data signal is handed over from one Atmel ATA6836C to the next one stepwise as long as the CS signal remains low. This causes, however, longer reaction times since several programming cycles are needed to load the designated setting into each Atmel ATA6836C. The DI pin of the first IC acts as input for all ICs while the DO pin of the last IC serves as output for the entire chain. The data word for the last IC has to be sent first, followed by the data word for the second-to-last IC, and so on. 9246C-AUTO-03/15 Figure 1. Daisy-chain Operation with Microcontroller and Watchdog VCC Enable Trigger Reset Watchdog Microcontroller INH INH ATA6836C ATA6836C CS DI DO CLK CS DI DO CLK VCC 2 ATA6836C/ATA6838C [APPLICATION NOTE] 9246C–AUTO–03/15 CS DI DO CLK INH ATA6836C CS DI DO CLK INH ATA6836C CS DI DO CLK 1. Basic Daisy-chaining Principle Table 1-1 shows the basic principle of how data words are shifted through daisy-chained ATA6836C ICs. Unlike with other Atmel driver family members, (nx2)-1 shifts are needed for writing a command into the n. Atmel® ATA6836C IC. Table 1-1. Basic Method of Shifting Data Words through Daisy-chained Atmel ATA6836C ICs I/O Cycle 1 2 3 4 5 6 7 IC Number 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 DI A x x x B x x x C A x x D B x x E C A x F D B x G E C A DO x x x x x x x x A x x x B x x x C A x x D B X x E C A x 2. Revision History Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this document. Revision No. History 9246C-AUTO-03/15 Put document in the latest template ATA6836C/ATA6838C [APPLICATION NOTE] 9246C–AUTO–03/15 3 XXXXXX Atmel Corporation 1600 Technology Drive, San Jose, CA 95110 USA T: (+1)(408) 441.0311 F: (+1)(408) 436.4200 | www.atmel.com © 2015 Atmel Corporation. / Rev.: 9246C–AUTO–03/15 Atmel®, Atmel logo and combinations thereof, Enabling Unlimited Possibilities®, and others are registered trademarks or trademarks of Atmel Corporation in U.S. and other countries. Other terms and product names may be trademarks of others. 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