Drop-in Microcontroller Board （1）

Published:2011/7/27 21:29:00 Author:Phyllis From:SeekIC

An 80C32 jack-of-all-trades

At the heart of this remarkably compact microcontroller board you’ll find an ingenious bit of integration technology. The combination acts as a versatile plug-in module for lots of applications requiring some form of intelligent control. Thanks to the extensive software that comes with the board and the presence of a PC interface, our drop-in board is excellent for hardware development, too.

As many of our readers will be able to confirm, the majority of microcontroller boards look very similar. If the microcontroller used has no program memory, an EPROM is added. Similarly, if there is a lack of RAM, the problem is solved by adding an external RAM device like the 62256. The lot is then complemented with a few logic gates and hey presto we have a basic microcontroller system. In some cases the designer will go one step further by employing a little more than just the microcontroller I/O pins. Some more digital electronics is then in order, but that really wraps it up as far as the circuit is concerned.

PSD813 series

Okay, if all these microcontroller circuits are so similar, why not design a single integrated circuit that contains all functionality? That way, circuits can become much smaller and the designer could concentrate on those points that are unique to the circuit. This, we figure, must have gone through the heads of several designers at STMicroelectronics (formerly SGS Thomson), the general idea having culminated in a series of ICs called ’PSD813xxx’. The individual components inside the chip are found back in Table 1. Obviously, this IC offers far more possibilities for a wide variety of microcontroller circuits.




Figure 1 shows a block diagram illustrating the internal structure of the PSD813xxx chips.




The memories may be mapped on a segment by segment basis. This creates many different configurations, for example, first 16 K Flash, followed by two 8 K EEPROM segments and then another 32 K of Flash memory.

The memory management is also very handy. For example, using the page registers allows you to increase the controller’s address range. Another possibility is to configure the memory in a different way depending on the page register contents. The samples show how this is done in practice.

The CPLD section in principle obviates the logic that’s normally required to drive peripheral devices, but only if the designer is satisfied with 27 I/O pins. For a controller with a multiplexed bus, this allows a de-multiplexed address to be created by the chip and, if necessary, a tri-state databus. Other applications include generating chip select signals for the peripheral devices or even creating extra I/O ports.

The PSD813 series has not been designed for one specific family of microcontrollers. In fact, it is so versatile that it can be used with several microcontroller families. These include not only micros with a standard address bus and databus, but also types with a multiplexed data/address bus like the 80C32, 8051XA and the 68HC11.
One final point to mention in this short profile is the JTAG port that allows all functions of the chip to be programmed in-circuit. In other words, it is not necessary to buy an expensive programmer — and that’s good news.

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