Product specifications

FILE ALLOCATION
Sharp Electronics Corporation
Section-3: More on Memory Allocation
IMPORTANT: Memory File Allocation – Must be determined before any extensive PGM2 Mode
Programming is started.
1. Overview:
In order to store programming and sales data, not only must space in memory be available,
but also the logic circuitry must know exactly where in memory it resides in order to retrieve
it on demand. If an additional number of functions (such as increasing the number of PLU
items from default, or the “out of box” number) were to be made available, additional RAM
has to be added to the register to hold this information. Until a few years ago, RAM
additions to the register were mounted in specific RAM slots, depending upon the function
that was to be expanded. For example, if PLU items were to be expanded, the chip had to
be mounted in the RAM slot that was used for PLU items.
The limitation of additional memory chips to specific functions is a disadvantage because
the unused portion of the chip could not be used for anything else. If another function, such
as “Previous Balance Files”, was to be expanded, a “PB” chip had to be installed even
though there may have been sufficient unused memory on the “PLU” chip.
To solve this problem, the method of memory access in the register was changed so that if
an optional RAM chip was installed, the memory in that chip could be used for any purpose.
Instead of designating the whole chip to a function, separate portions of the memory area of
the chip are set aside for any of the functions that can be expanded, utilizing the chip’s
storage capabilities.
Memory in this type of register is seen by the logic as one continuous block of addresses.
Additional memory added to the register takes up where the last address of the previous
chip left off resulting in a larger block.
Before any portion of the memory can be utilized for storage of a specific function, the logic
must know how large a block of the memory area needs to be set aside, or “allocated” for
that function.
Memory is allocated for each function by programming. This programming references the
File Allocation Table (FAT) which provides the following information:
• A list of the files that are in the register (FDS records)
• Each file’s maximum and minimum expansion limits
• The default size of each file
• The amount of RAM memory (in bytes) required for each function
• Each file’s reference number (Table or Group #) used for programming
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