Page 113 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Unit 7: Memory Interfacing

With the development of affordable EEPROM, EAROM and eventually flash memory, it became Notes
practical to attach the controller permanently to the board and to download program code to it
through a serial connection to a host computer. This was termed “in-circuit programming”. Erasure
of old programs was carried out by either over-writing them with a new download, or bulk
erasing them electrically (for EEPROM) which was slower, but could be carried out in-situ.
The main function of the controller board was now to carry the support circuits for this serial
interface, or USB on later boards. As a further convenience feature during development, many
boards also carried low-cost features like LED monitors of the I/O lines or reset switches mounted
on-board.
• 8748

• PIC
• Atmel AVR
7.4.10 Single-board Microcontrollers Today

Microcontrollers are now cheap and simple to design circuit boards for. Development host systems
are also cheap, especially when using open source software. Higher level programming languages
abstract details of the hardware, making differences between specific processors less obvious to
the application programmer. Rewritable flash memory has replaced slow programming cycles,
at least during program development. Accordingly almost all development now is based on
cross-compilation from personal computers and downloads to the controller board through a
serial-like interface, usually appearing to the host as a USB device.
The original market demand of a simplified board implementation is no longer so relevant to
microcontrollers. Single-board microcontrollers are still important, but have shifted their focus to:
• Easily accessible platforms aimed at traditionally “non-programmer” groups, such as artists.
These controllers may be embedded to form part of a physical computing project. Popular

choices for this work are the Arduino, Dwengoor the Wiring project.
• Technology demonstrator boards for innovative processors or peripheral features:
– AVR Butterfly
– Parallax Propeller
Figure 7.9: Single-board Microcontrollers Today

Flash Memory Analyzer

he integrity of a Flash memory device degrades over time primarily due to the impact
of erase cycles. Wear-levelling techniques are internally employed by the device to
Tslow its degradation and prolong its life span. Our product, the flash memory analyser,
allows a variety of flash memory devices to be subjected to stress tests and their aging to be
Contd...

LOVELY PROFESSIONAL UNIVERSITY 107