As real computer is not a real computer without a real time clock, the Steckschwein is no exception here. As we know, we use the Maxim DS1306 RTC, which is a very common RTC which comes as DIP IC and has an SPI interface. And of course it supports battery backup in various configurations. And this is where things get interesting.

Apart from timekeeping, the DS1306 also has 96 bytes of battery buffered RAM. The ideal place to store system configuration parameters. As of now, the RTC NVRAM contains the name of the file to be read from sdcard at startup, the line parameters for the serial interface (baud rate, data bits, parity, stopbits), and also a version number and a crc7 checksum:

The Tekway DST 1062B (also known unter the Hantek or Voltcraft brand) is an inexpensive 60MHz digital storage oscilloscope, which is very much hackable and has proven to be worth its weight in gold pressed latinum.

More recently, my scope became affected by the infamous white screen problem, which apparently is a problem quite common to this model and its 100MHz or 200MHz siblings.

The Tekway/Hantek white screen of death

The newly made boards made their way from China to Munich. Starting now, the multi board version of the Steckschwein is made up of 3 Boards: CPU/Memory, IO/UART and V9958-OPL2.

It’s time for another hardware upgrade. Since we really want to get our single board Steckschwein done, we are going for higher integration of our multiboard prototype. After integrating the UART to the IO-Board, we integrate the OPL2 sound part onto the V9958 video board, so the current Steckschwein multi board incarnations are reduced to three boards. We did postpone our plan to upgrade sound to OPL3 because Daniel Illgen, which we met at VCFb, convinced us with some awesome OPL2 tunes that OPL2 is still cool. Also, we save the extra oscillator, since the OPL2 can be clocked using the CPUCLK-Pin from the V9958, which happens to provide 3.58MHz.

… on the way back to munich, we had some time to do a little code review of our gfx library. thinking about the cpu to video chip timings and again read the well known datasheets of the V9938/V9958. suddenly i got an enlightenment and we came to the following conclusion.

as described in the datasheet (V9958-Technical-manual_v1.0.pdf) of the V9958 there are different timings given for different kind of writes. so as far as we understand there are the following timings

The woz monitor, also known as WOZMON, is a pretty simple memory monitor and was the system software located in the 256 byte PROM on the Apple I. Wozmon is used to inspect and modify memory contents or to execute programs already located in memory. Steve Wozniak managed to squeeze all that functionality into 256 bytes. That’s right, bytes. Not megabytes, not kilobytes. Bytes.

We already had attempted to get wozmon ported to our Steckschwein, but we did not succeed so far. That might have been because the wozmon-code is a little bit hard to read and makes use of some Apple I specific things, which we did not know they were, since we do not have any expertise about the Apple I.