79228942EE200v01| Application Note
Engineer-to-Engineer Note
EE-200
a
Contributed by B. Lerner
Technical notes on using Analog Devices DSPs, processors and development tools
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ADSP-TS20x TigerSHARC Processor Boot Loader Kernels Operation
Rev 1 March 4, 2004
Introduction
This EE-Note explains the functional operation of the power-on booting procedure and the boot loader kernels for the ADSP-TS20x TigerSHARC family of processors. This EE-Note focuses on kernels for ADSPTS201S and ADSP-TS202S processors. Kernels for ADSP-TS203S processors form a subset of the discussed functionality because this processor has only two link ports and a 32-bit external bus. Except for these restrictions, the following information applies to all ADSPTS20x processors.
processor's booting modes. Additionally, there are several no-boot modes, which do not require kernels.
Booting Procedure
The booting mode is selected by the processor's /BMS pin. While the processor is held in reset, the /BMS pin is an active input. If /BMS is sampled low a certain number of SCLK cycles after reset, EPROM boot mode is selected; a number of SCLK cycles after this, the /BMS pin becomes an output and serves as the EPROM chip select. If /BMS is sampled high instead, the ADSP-TS20x processor will be in an idle state, waiting for a host boot or a link port boot to occur. The exact timing for sampling /BMS boot strap and following driving of /BMS is provided in the processor's data sheet [3]. Additionally, a weak internal pull-down resistor is on the /BMS pin. Depending upon the external line loading on this pin, this pull-down resistor may not be sufficient,. Thus, you may need to add an external pull-down resistor to select EPROM booting mode. If host or link boot is desired, /BMS must be held high during and after reset and may be tied directly to VDD_IO, provided it is never used as a chip select. Each booting me
thod is described in detail in the following sections.
Loader Kernels and Boot Modes
A loader kernel is a program executed by the processor that is appended to user application code by the elfloader utility (elfloader.exe) of the VisualDSP++ development tools. The processor executes the loader kernel processor at boot time, allowing the processor to initialize its internal and external memory sections defined in the application code. The loader kernel is a self-modifying program that is transferred into the processor's internal memory. The ADSP-TS20x family of processors supports three booting methods: EPROM booting (via the external port), host booting (via an external host processor or another ADSP-TS20x processor), and link booting (via the processor's link ports). VisualDSP++ includes three distinct loader kernels that support each of the
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