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MaxLoader User’s Guide
25
reprogrammed like EPROMs. These ICs are called erasable programmable
logic devices or EPLDs. Internally, they have the same programmable AND-
OR-register structures of the PAL and FPLA.
Microcontroller
These devices are CPU's with on-chip EPROM and RAM. They are typically
40 pins and are UV erasable. They have part numbers such as Intel's
8748,8749,8751,8752 etc. A micro-controller is generally a computer-on-a-chip
with RAM, ROM, and I/O ports. Microcontrollers are usually used for specific
purposes, such as keyboard decoders, printers, clocks, telephones, CD-players,
or any other application that requires a small, on-board computer.
Microcontrollers are used to take the place of in-circuit logic, as it can be less
expensive and take less space. Also, since it is software driven, the device may
be updated very easily. Micro-controllers have the ability to use internal as well
as external RAM. Also, micro-controller data may be encrypted or otherwise
secured to prevent copying of the data or program information. Microcontrollers
also have their own instruction set, usually very similar to familiar
Microprocessors (such as the 8080 or 8086). The INTEL MCS-51 family
features up to 64k each of internal and external memory, 32 I/O lines, interrupts,
timers, and bit-addressable RAM. Its instruction set contains 111 instructions.
However, for specific purposes, limited versions of the 51 family are available.
For instance, the Philips 87c751/87c752 families do not allow external RAM to
be used, and have limited I/O channels, etc. However, these devices still allow
for data/program encryption and security levels. They are also less expensive
than the MCS-51 micro-controllers.
See the help selection under MAIN-MENU COMMANDS for Encryption and
Security-bit information.
NOTE: Programming Microchip PIC family Microchip
PIC series are different from other Microcontrollers in that they have an
EPROM area as well as a Configuration Fuse. The Configuration Fuse in the