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I am trying to measure the output impedance of an opamp in the attached configuration. Results are attached.
Basically, Zo = Vo/Io = 10mV/40mA = 0.25 Ohms.
Without the capacitor in the circuit, I get mostly a large dc current. Is there a better method to measure output impedance? I would like...
Okay. The third byte in the BIOS after the 55 AA is "30". From what I found, this 30 indicates that the length of the ROM = 30 * 512 = 6000h. However, the code clearly jumps to locations beyond 6000h. How is that possible? My ROM is storing the odd bytes first and then followed by even bytes...
Thanks! Do you know for sure that in the 32k ROM the checksum is stored at 5FFF? Remember, this ROM is 32k, and all the odd bytes are stored in the first 16k and the even bytes are stored after the 16k.
After a long break.
I am trying to plant a code in the VGA BIOS that I will be able to call later after I bootup in to MSDOS. I tired putting the code in the location where the copyright notice was written - but did not work. BETWIXT has already mentioned the reason for this not to work. I am...
I am guessing that the system BIOS also writes values in to the registers inside the VGA chip when the video mode is changed (Int 10h). Right? I am only trying to see what values are being written in to the 3C2 register by the BIOS (VGA or system).
Thanks.
Thanks!
I am looking for values the VGA bios writes to the control register, 03C2. I will be dissembling the code today. I found only 4 locations in the complete ROM which refers to this address register and I believe its an OUT instruction."BA C2 03"
Thanks for all your help. Your comments...
That is an excellent catch. I was the 55 that was common. Did not catch the even and odd byte business. However, I am 100% sure that there is only 1 bios chip. The board as only 3 other chips - 2 RAMs and 1 VGA controller.
There is another BIOS on the motherboard, but, that should not...
Thanks.
This is the first 5 lines from the programmer -
:100000005530FA4FA8000000FE7100302F353949F5
:100010004D434D41494C0A6865695645286D204756
:100020002D6F70746265424F2065736F20200D4301
:1000300070726774282931382D3930506F6E7854BA
:10004000636E6C676520742E0A6C20696873527346
If I look at...
The ROM is 32 kilo bytes.
I have not been able to open the 650 MB file on the Windows system. Its got no network cards and I cannot transfer the file (I can fix that somehow).
I don't understand why its 650 mb. I am assuming that the text format takes up much more space than the simple HEX...
Thanks Brian.
I could see the 55 and AA in the code when I did debug -d C000:0000. However, they are not visible when I use an EPROM reader to read the data from the chip. The card I am talking about has its own video controller- its called ACUMOS AVGA1.
So, you think the VGA BIOS is not...
Thanks Brian. That makes perfect sense. I forgot to mention that I am looking at the VGA BIOS on a graphics card made in the 90s. I did a hex dump using the debug command from C0000 to C7FFF from the RAM (took several hours to complete). The file is 650 MB. I will try to analyze it. The VGA Bios...
Is there a BIOS/EPROM programmer/software that can do the de-compression and give me the HEX files which I can disassemble?
How do I find out what format is being used to compress the code in my BIOS?
I was wondering if there was some coversion to do before feeding the intel hex output from the programmer to the disasembler.
Can you recommend a good disassembler?
What is the format of the data that I read from the EPROM using a programmer? How do I convert this to assembly language?
As far as I can see, the output from the programmer is Intel Hex format, and has all the fields indicated by the format.
But, I cannot find the same hex codes that I see...
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