Search found 18 matches

by jwolfram
16 Feb 2020, 09:08
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

Re: Expansion bus

I think, there are two ways. The first needs additional hardware, for instance 3 AND gates. MISO2 = (CS0 & CS1) & SDA MISO3 = (CS0 & CS1) & SCL this ensures that MISO2/3 are low during SPI transfer. On the other hand it should be possible to held SCL and SDA low in idle state. The only restriction i...
by jwolfram
12 Feb 2020, 07:26
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

Re: Expansion bus

My first draft has the advantage that it don't need any modification on the expansion module. One disadvantage are SCK pulses during I2C communication. This is because SCK must be set to one to read the status of the MISO lines. If the SS line is high (SPI slave is not selected), this should be no p...
by jwolfram
11 Feb 2020, 07:23
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

Re: Expansion bus

A test with a 4GB SDHC card seems OK. I copied mosaic.gt1 to the card and renamed the file to system.gt1 and now all seems to be OK. But I have seen that the CMD58 result on the screen is still 00. As far as I know, bit 6 should be set for SDHC cards. And there are further ideas... With adding two a...
by jwolfram
10 Feb 2020, 12:13
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

Re: Expansion bus

I've not understand the card detection code completely but I have looked at a former project of me (AX82). SD cards (also SD V2) are addressed "per byte" and SDHC cards "per sector". They differ in the answer of CMD58. SD cards will return with bit 6 is zero and SDHC should return a result with bit ...
by jwolfram
10 Feb 2020, 10:59
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

Re: Expansion bus

Last weekend I tried to implement the SPI routines tom my "Micro-" Emulator. Everything seems to work, but I'm no able to get my SD card working. It is a 2GB SD-Card (not SDHC), formatted with fdisk and mkfs.vfat -F 32. But I get always "Vol.ID 0000 Failed". Is there a special treatment to get this ...
by jwolfram
07 Mar 2019, 09:14
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 17965

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: 96
Views: 17965

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: 96
Views: 17965

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: 96
Views: 17965

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: 96
Views: 17965

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: ...