Browse Prior Art Database

DYNAMIC EPROM SIZE DETECTOR

IP.com Disclosure Number: IPCOM000006331D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-25
Document File: 1 page(s) / 83K

Publishing Venue

Motorola

Related People

Glenn Mayer: AUTHOR [+2]

Abstract

Computer/Microprocessor cores arc often designed to support several different types of memory devices, including EPROM/ROM, RAM and EEPROM. Com- plex processing elements typically support large mem- ory address spaces, requiring several 'banks' of memory devices to till the address space. In order to expand the available memory as the application software grows, the hardware typically supports several sizes of memory devices so that higher density devices can be used. As a result, the software needs to know what size device is installed so it can properly utilize the available memory space.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

DYNAMIC EPROM SIZE DETECTOR

by Glenn Mayer and Mark Spiotta

   Computer/Microprocessor cores arc often designed to support several different types of memory devices, including EPROM/ROM, RAM and EEPROM. Com- plex processing elements typically support large mem- ory address spaces, requiring several 'banks' of memory devices to till the address space. In order to expand the available memory as the application software grows, the hardware typically supports several sizes of memory devices so that higher density devices can be used. As a result, the software needs to know what size device is installed so it can properly utilize the available memory space.

  RAM device sizes can be easily detected due to the inherent read/write capabilities of random access mem- ories. Unfortunately, ROM devices can not be sized in a similar fashion because they are read-only devices. As a result, ROM device sizing is usually manually determined either by jumper or switch settings on the module, or by configuration information stored in non- volatile memory. The problem is that these methods require manual intervention to set the device size in order to match the memory map decoding to the actual devices installed. This additional process step can be a source of defects in the manufacturing cycle. Alternately, EPROM device configurations can typically be read directly from the device by applying high voltage (- 12V) to one of the address lines. Unfortunately, this approach requires additional circuits to generate the high voltage and to multiplex the functionality of the special address line.

  The purpose ofthis technique is to detect the size of each bank of ROMs in a processor memory space and adjust the memory map decoder for each bank in order to provide a contiguous memory space available to the processor. This detection is automatic and requires no jumpers, switches, or additional components to indicate the size ofthe memory device.

It is assumed that the processor has control over the memory m...