Search found 13 matches

by jwolfram
07 Mar 2019, 09:14
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

Transfer a fixed number of bytes is suitable for writing to a SD card but not for reading. For init (must be do at low frequency) and read we need polling. I will explain how I did SD-card access in my library: Read sector: set CS to LOW send 2 times 0xFF (dummy, for sync) send 0x17, address and che...
by jwolfram
03 Mar 2019, 10:24
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

Yesterday I started with a concept to add this to my emulator. An I found two topics which are IMHO worth for discussion. At first, the MOSI line. I think its better to get it from A15 instead of A7. If You use A7, the data to output must be build from bit 7 of the data to shift and the control line...
by jwolfram
01 Mar 2019, 21:30
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

I think, the shortcuts between BUS0/BUS4... are not so good.

Joerg
by jwolfram
25 Feb 2019, 08:43
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

Marcel, I think Your idea with the $?? operand is excellent. It should make it possible to do I/O without touching RAM and probably to avoid glitches. Here are some new thougths: - WE_RAM is /WE OR NOT(OE) to prevent write to RAM at this commands - IOSEL is active if /WE and /OE low and registers th...
by jwolfram
22 Feb 2019, 07:39
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

Further thoughts: 1. My emulation is not fast enough to distinguish between RAM and SPI acess, so its a good idea to use an 'unique' command for SPI access. For instance, ora [y,x]. This operation is currently not used by the GIGATRON ROM and there is no problem with compatibility. 2. For Note 14: ...
by jwolfram
21 Feb 2019, 20:38
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

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...
by jwolfram
12 Feb 2019, 09:54
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

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...
by jwolfram
30 Jan 2019, 09:32
Forum: Hardware and software hacking
Topic: Gigatron emulator in a µC
Replies: 2
Views: 376

Re: Gigatron emulator in a µC

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...
by jwolfram
23 Jan 2019, 09:15
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

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
by jwolfram
15 Jan 2019, 12:49
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 49
Views: 2979

Re: Expansion bus

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 done at start...