Tektronix TDS210/220/224 are entry level digital oscilloscope, it needs a TDS2MM measurement extension module to support some additional measurements functions such as FFT, pulse rising/falling time, and pulse positive and negative width etc. TDS2MM module is not easy to find, it can be reworked from TDS2CM which is still expensive these days. I managed to reverse engineered a TDS2MM module and created an equivalent module which can enable these additional measurement functions, however, it doesn’t come with any communication function (GPIB/UART/Parallel).
Schematic is attached, this module consists of a Flash, a SRAM, a PLD, two 8-bit bus transceiver, and a 50-pin connector. The PLD is the key of this module, it has three functions: address decoder, bus transceiver direction control, and GPIB/UART emulator. The original TDS2MM module has a GPIB controller and a UART transceiver, the scope will check the status of these two transceivers during boot, if any of them was not detected correctly, the module will be considered as not installed.
the picture of this module is as below, it can be inserted into a blank module cover, a TDS2CM module cover, or you can insert it into the scope extension slot directly if you don't have the cover, it just works fine.
The parts list are as below, if you want to use different part, be careful about the timing, especially the PLD, the image is for that specific part, it may not work for other PLDs. For RLASH and SRAM, the latency should be < 70ns:
FLASH: SST39SF040-55-4C-NHE-T
SRAM: IS62C1024AL-35QLI
PLD: ATF16V8BQL-15JU
Bus Transceiver: SN74AHCT245DW
50-pin connector: A3-50DA-2DS(71)
If you have a TDS210/220/224 scope and don’t have TDS2MM module yet, you can create one with all the files I have shared, it’s going to be a fun project, enjoy!