Tekmos Programmers

Tekmos makes replacements for legacy microcontrollers, and many of them used EPROM for program storage. EPROM was the first technology that was user programmable, though it was replaced first by EEPROM and later on by flash. Nowadays, it is very difficult to even find a foundry that offers the EPROM technology. When faced with a need for EPROM storage, Tekmos decided to use flash memories, in a stacked die package configuration. This works quite well in the application, but it does require a different programming algorithm. And that is where things become complicated.

ekmos uses the same 4 MB flash memory in each of our devices. But the devices differ in how to access it. The simplest method is used in the TK89C668, which uses a test mode to bring out every pin. The 68HC05 and 68HC11 series are more complicated. These chips did not have the test mode used by the Intel controller families. Instead, they have a bootstrap mode. This requires the loading of a small program into RAM, and then using that program to program the flash memory.

Tekmos has received much appreciated support from Elnec in having their programmers support our parts. But we make a lot of parts, and so we had to develop programmers to support those parts who are only sold to a limited number of customers.

Tekmos programmers are based off of the Raspberry Pi computers. These are readily available and well supported with cases and other accessories. The Raspberry Pi is a 3 volt system, and almost all of our controllers are 5V devices. So we designed an adapter card that translated the 3V signals to 5V, and back again. We use this card in all of our programmers. And on top of this card, we designed a third card that holds the specific socket for the device we wish to program. This third card may also hold a DC to DC converter for those devices that require a 10 volt signal to get into the programming mode. We took a standard Raspberry Pi case, had a hole cut in if for the socket, and we were done with the hardware.

One of our engineers wrote a program that reads the programming files, downloads a bootstrap program, and then programs the parts. And now we have a programmer.