Gigatron Hackers

Some further explanantions: Note 5: You're using A10 below, but this memory initialisation pivots around A11. Is this a small oversight? Yes, that's right. I wrote this down before the idea of double use of A10 was born. Note 13: Is that why A10 is having the double function? To avoid glitches? But...

Yesterday I tested it, my test cycle (init, write a sector, read back) works at both 15KHz and 30KHz. I tested 2 cards, a 2GB SD card and a 4GB SDHC card, both are approx 4-6 years old. So it should be possible to make a half or a complete SCK clock cycle per video line. I hope, this information hel...

Hi Ken, at the beginning, I started with 175MHz which was only slightly above the 168MHz. The most timing critical instructions are the conditional branches. They require branches on the host side which causes additional wait cycles. With a small test program and some measuring I found out, that 225...

I can make a test next time to determine which is the lowest speed for communication with the SD cards. But I think, only the upper limit is important.

Joerg

The frequency limitation is only valid within the init phase, after the init is done, You can use SPI frequencies up to 20MHz and more. My suggestion is to use an image file, which contents a number of "0-padded" GT1 files of, for example, 64K or snapshots. During init, which should be don...

Some further ideas: Hardware: - 64K (128K) RAM is mandatory, probably it should be possible to make the upper 32K switchable if a 128K RAM is used - Fill at startup 0xF000 to F7FF with 0x01, 0xF800 to 0xFFFF with 0x00 - /IOSEL decoder with 74xx30 /IOSEL = /(A11 & A12 & A13 & A14 & A1...

Some thoughts... Another idea is to use only pages 0xFD-0xFF. So 63K of RAM can be used and it needs only a 74LS30 etc. to decode. I prefer SPI as communication protocol, so also SPI EEPROM/FLASH can be used as external storage. If one of the the pages is selected, a ld[y,x] can register 2 chip-sele...

Hello, a new Gigatron emulator is alive: http://www.jcwolfram.de/projekte/gtmicro_en/main.php It emulates a cycle accurate gigatron with 64K RAM in a overclocked STM32F405, the 'external' hardware is nearly identical to the original (except for the lower voltage levels). gigatron_tinybasic2.jpg