Find a way to break up the data into short chunks at the PC end and send those one chunk at a time to the MCU. Make the chunks small enough to that one will fit into the RAM of the MCU. Then implement the JTAG process to the CPLD for that chunk. Upon completion then send a completion ACK back to the PC whereupon it will pick up and send the next chunk of data.

To be able to create this successfully you will need to be intimately familiar with the CPLD programming file content and its format. You will also have to 100% comprehend the CPLD's programmng protocol via the JTAG interface. Many vendors of CPLDs have application notes at their web sites that describe this information for their particular devices.

There are also one or more CPLD vendors that have sample code to go with their application notes that show how to do this. It is typical for these applications to show the PC doing the complete programming task via some type of JTAG pod connected directly to the PC. If this is the case with your CPLD vendor you will have to break that protocol into two parts..one for your MCU and leave the other higher level part for the PC.

Michael Karas