Developing Programmers

Many of the microcontrollers that Tekmos makes were originally OTP parts that contained EPROM.  The EPROM process is not available in our fabs, so we replace the EPROM with Flash memories.  This is totally transparent in the user application, and has the added advantage that we can reprogram them if necessary.

The one difference in using a Flash memory is that Flash requires a different programming algorithm.  And since the old EPROM algorithm uses high voltage, any attempt to program our parts with the old algorithms will destroy them.

Some programming companies support some of our parts.  But the increasing widespread use of ISP (In-System Programming) has greatly reduced the demand for programmers, and that has reduced the amount of support we can get from the programming companies for our products.

As a service, we pre-program parts for some of our customers.  We include it in the production final test, where it fits easily into our manufacturing flow.  But this doesn’t work for everyone, including military customers with secret code.

So we have decided to support our programmable devices with “engineering” programmers.  These are not really set up for a production environment.  Instead they are a small PC board with a USB connector, a socket, and a few chips between them.  We will have to create one for each of the programmable devices we make.  And that is about 9 boards.

We chose to have a common interface to the PC.  Rather than invent one, we chose to use the existing ISP protocol, but with a few more commands to turn the programmer on and off.  This reduces the programming tasks at the PC end.

The board consists of a USB to UART chip that is connected to a micro, which goes to the socket.  Within the micro, the code that talks to the PC is a constant, and the only thing that varies is the interface to individual processors.  And that varies a lot, since each programmable device has a different interface.

Our most popular processor has an ISP interface, so the programmer is just a 1 to 1 interface between the PC and the chip.  In other micros, we put it into a test mode, the internal flash pins are brought out, and we program it just as we would a regular flash memory.

The 68XX micros pose a more difficult challenge.  We put them into a bootstrap mode, and download a small program that allows us to read and write to any address.  This program then allows us to write to and read from the control registers for the flash and for the internal EEPROM.

We are bringing up our first programmer for the TK68HC711D3 device.  Once that is done, we will work on the others.  These are slated for a 1st quarter introduction.  

Date

2013-11-06