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Application Note
JTAG Flash Memory Programmer
AN1264
MOTOROLA, 1995
Microprocessor and Memory
Technologies Group
SEMICONDUCTOR PRODUCT INFORMATION
By James Gilbert, High Performance Embedded Systems, East Kilbride.
During the manufacturing process for the production of embedded processor systems, there is no firmware
present in the on-board memory. While some manufacturers get the required software masked into ROM during
the device fabrication, this is commonly expensive and certainly more restrictive in terms of new software
releases. A more flexible approach is for the system manufacturer to upload the system software during their
production cycle. To do so, means the system hardware must have a communication interface build into it. With
pcb space at a premium, a serial interface is the preferred choice.
Some processor families offer a solution through their in-built serial debug interface. Examples are the CPU32,
CPU32+ based MC683xx family, the embedded Powerpc MPC5xx/MPC8xx families and the MCF52xx Coldfire
family, which utilise a background debug interface to allow a pc/sun host to remotely debug and control the
processor and thereby the system. This is great in the flexibility and production time download stakes, but
different processor manufacturers adopt their own particular serial implementation.
An alternative which is often overlooked is the JTAG interface. Many manufacturers consider IEEE1149 JTAG
Test Access Port as mandatory for system and integrated circuit integrity testing using automatic test
equipment. As such it is already present in the system, and so is an ideal candidate for a firmware loading
mechanism. The download speeds possible using JTAG may prohibit its practicality for downloading the
complete system software, but certainly it is ideally suited to download a small bootloader program into Flash
EPROM to control the remainder of the system download. Another key application area the technique supports
are field upgrades where new software releases are loaded onto an existing customer system.
This document describes a JTAG Flash EPROM programmer designed to run on an IBM compatible PC. While
the programmer was tested using MC68307 and MC68306 processor systems, simply changing the two scan
register input files makes the programmer equally applicable to any (well at least many) other processor with a
JTAG IEEE1149.1 compliant port.
ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2006
