Eeprom write with timeout?

[+karri]

Most of my code appears to hang on various systems that lack the eeprom.

I wonder if anyone has written a driver for 93c46 chip with a built-in timeout?

 

Currently the driver waits for a handshake signal to see that the write cycle is complete. But according to the datasheet the maximum time for a write is 2ms. So I was thinking of just adding a few NOP's to delay the process slightly and skip the polling.

 

The tick is 62.5 ns so I may need to sleep for 32000 ticks.
What is the best way? Interrupt after 32000 ticks, use a timer, NOPs, listen on VBL interrupts and write one word per VBL?

 

This could also be handled in user space.

write(addr, val);
delay();

if (read(addr) != val)
    return NO_EEPROM;
return OK;

 

Any ideas?

[laoo]

One word per VBL should be bulletproof. And given that you won't write more than 60 words also unnoticeable for users.

 

[+karri]

3 minutes ago, laoo said:

One word per VBL should be bulletproof. And given that you won't write more than 60 words also unnoticeable for users.

 

Makes sense. Usually I just may need to write two bytes at the end of a level (high score).

[sage]

3 minutes ago, karri said:

Makes sense. Usually I just may need to write two bytes at the end of a level (high score).

just take the HBL counter

[laoo]

Rule number one of engineering: don't over-engineer ?

I just made it up, but the truth is that simplest solutions tend to be the best.

 

[sage]

HLB counter tick is 100us even for the highest framerate the lynx supports.

[+karri]

I might go with the cc65 clock() function. It maintains something called clock_count. It is a 3 byte data that gets incremented at every VBL.

So if I just wait for the lowest byte to change twice I should be safe. Always.

 

... bad thinking ...

It requires the game to actually use clock().

 

Perhaps I go with HBL after all...

[+karri]

I hope this is the way to do the 2ms wait in asm.

 

; 2ms wait
        ldx #20
EE_wait1:
        lda HTIMCNT
EE_wait2:
        cmp HTIMCNT
        beq EE_wait2
        dex
        bpl EE_wait1

At least it compiles...

 

On a side note I may maintain a master copy of the eeprom in RAM and if the eeprom fails I just don't care.

static unsigned int eepromdata[64]; 
unsigned char haseeprom = 1;

unsigned int eeprom_read(unsigned char pos)
{
        if (haseeprom) {
                eepromdata[pos] = lynx_eeread_93c46(pos);
        }
        return eepromdata[pos];
}

void eeprom_write(unsigned char pos, int val)
{
        eepromdata[pos] = val;
        if (haseeprom) {
                lynx_eewrite_93c46(pos, val);
                if (val != lynx_eeread_93c46(pos)) {
                    haseeprom = 0;
                }
        }
}

 

 

[+karri]

My logic was obviously flawed. I may need to poll for 20 complete cycles of horizontal scan lines instead of 20 ticks. Sigh...

[laoo]

Yeah, a value of vcount should polled, not hcount. One line take 159 us for 60 fps refresh rate so 20 lines is 3.18 ms.

 

You can try running it in Felix with logging on (running through lua file with logging set). It can tell about eeprom status. And you could test emulation in Felix at the same time

Edited November 4, 2021 by laoo

[+karri]

1 hour ago, laoo said:

Yeah, a value of vcount should polled, not hcount. One line take 159 us for 60 fps refresh rate so 20 lines is 3.18 ms.

 

You can try running it in Felix with logging on (running through lua file with logging set). It can tell about eeprom status. And you could test emulation in Felix at the same time

The vcount way works ok in Mednafen and on a real Lynx with an eeprom chip. But it still freeze when it tries to read the eeprom on Felix.
I am a bit new for Windows. Currently I have a Win 11 installed in my laptop but I tend to use Ubuntu over VMware.

I should probably start looking for lua and compilers for running something on Win11.
Currently I am running some Epic Unreal. But it is high level stuff - no code.

[laoo]

You don't need anything. Felix has embedded lua interpteter. To "debug" in Felix you just need to create a lua file with the content:

 

lnx = "full/path/to/image/file";

Log{ path = "full/path/to/trace/file.log" };

Run Felix for a while (with this file instead of given lnx image) and close it. You will end up with HUGE trace file in given location.

 

Search in trace for lines with "EEPROM" text within.

 

Edited November 4, 2021 by laoo

[+karri]

My repo has an updated version of eeprom.s that waits for 20 scanlines instead of polling IODAT. The location in bitbucket.org/atarilynx/lynx.git and the file is in lynx/tools/cc65/libsrc/lynx/eeprom.s

[enthusi]

Dear Karri,

I have not yet tackled eeproms but intend to do so now

Why are there so many eprom*.s files in that folder and is there a source for eeprom access code (or is that THE best document/source already?)

Speaking of your branch of PCBs (of course!)

Thank you very much!

I have been absent from Lynx land for a while but never abandoned it, of course.

[+karri]

35 minutes ago, enthusi said:

Dear Karri,

I have not yet tackled eeproms but intend to do so now

Why are there so many eprom*.s files in that folder and is there a source for eeprom access code (or is that THE best document/source already?)

Speaking of your branch of PCBs (of course!)

Thank you very much!

I have been absent from Lynx land for a while but never abandoned it, of course.

@sage created a bunch of support files to lots of different eeproms. But currently everyone is mainly using the smallest one. 93c46

It has 16-bit words by default. And can hold 64 of them.

[enthusi]

Ok, makes sense! Thank you for clarification.Seems quite straight forward so far. Best wishes!