Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
SilverSolder:
Thank you @joeqsmith, that confirms the slow read speed of the 8080 and we should be in good shape with pretty much any old EPROM of the right size (or double size, love your trick).
Also got to love how the DMM says "HI" to you when it starts. How many other DMMs are that cheerful when they wake up? :)
SilverSolder:
More disassembler magic, this time using NSA's 'Ghidra' software reverse engineering (SRE) suite of tools!
Amazingly, the NSA has open sourced that tool and made it available for download here: https://ghidra-sre.org
This tool is so powerful, it turns the machine code back into a C program! - a "decompiler", basically.
This function is the first thing the 8505/6A does when it starts... you can clearly see it ending up in what looks like the program's main loop, after doing a couple of other things first!
--- Code: ---void RST0(void)
{
ushort uVar1;
short sVar2;
undefined in_L;
undefined *puVar3;
byte bVar4;
*(undefined *)CONCAT11(0xc0,in_L) = 0xff;
puVar3 = (undefined *)CONCAT11(0xe0,in_L);
do {
*puVar3 = 0xff;
bVar4 = (char)((ushort)puVar3 >> 8) + 1;
puVar3 = (undefined *)((ushort)puVar3 & 0xff | (ushort)bVar4 << 8);
} while (bVar4 != 0);
sVar2 = 0x452c;
do {
uVar1 = (ushort)sVar2 >> 8;
bVar4 = (byte)sVar2;
sVar2 = sVar2 + -1;
} while ((byte)((byte)uVar1 | bVar4) != 0);
disableMaskableInterrupts();
_DAT_ram_47fe = 0x41;
FUN_ram_0091();
DAT_ram_41fd = 0;
_DAT_ram_47fe = 0x48;
FUN_ram_2938();
_DAT_ram_47fe = 0x4b;
FUN_ram_01ed();
do {
_DAT_ram_47fe = 0x4e;
FUN_ram_0214();
DAT_ram_41f8 = 0;
_DAT_ram_47fe = 0x55;
FUN_ram_34a3();
_DAT_ram_47fe = 0x58;
FUN_ram_087d();
_DAT_ram_47fe = 0x5b;
FUN_ram_2201();
_DAT_ram_47fe = 0x5e;
FUN_ram_0e62();
_DAT_ram_47fe = 0x61;
FUN_ram_0eab();
_DAT_ram_47fe = 100;
FUN_ram_0962();
_DAT_ram_47fe = 0x67;
FUN_ram_0445();
_DAT_ram_47fe = 0x6a;
FUN_ram_26e0();
_DAT_ram_47fe = 0x6d;
FUN_ram_0500();
_DAT_ram_47fe = 0x73;
FUN_ram_2848();
_DAT_ram_47fe = 0x76;
FUN_ram_16b8();
_DAT_ram_47fe = 0x79;
FUN_ram_007c();
} while( true );
}
--- End code ---
garrettm:
--- Quote from: joeqsmith on February 08, 2021, 06:01:35 pm ---I did program up a few PROMs. These are Toshiba 27128-20s. Ethically, something just doesn't seem right about using them in the meter. I just mirrored the image to both the lower and upper bank.
--- End quote ---
That was a clever EPROM trick! Will the 200ns access time of the new EPROMs have any meaningful affect on performance, or is the 8080 too slow to benefit?
I am happy to see the meter working with the new firmware. Hopefully, with that and triggering over the bus you'll see much faster read speeds.
I finally got my GPIB up and going today. Turns out my USB to GPIB adapter is faulty, but I have a working RS232 to GPIB converter from IOGear that can do 57600 baud. I'm still learning how to control the 8506A and might need to adjust the dip switches on the Serial488A Bus Converter but I should have some data to share in the next day or two.
joeqsmith:
The 607 firmware effects some of the formatting of the serial data which required a few changes to my software to support it. Some things are still a bit odd. For example, when using binary format with the trigger set to anything other than T@, the meter will send 5 bytes. However, in the T@ mode, it adds a CR for some reason. The old firmware had odd behaviors like this as well.
Outside of that, I am not noticing any differences. Maybe they were just minor bug fixes or they made changes to features I am not using. Too bad we don't have some sort of change log.
The new PROMs won't have any effect on the performance. These Toshiba PROMs were the only virgin parts I had.
With the software working again, I had another look at the high speed mode. If I had to guess, the firmware makes a decision to ignore the command if the hardware doesn't support it. Except, if I try to enable it, then select the async internal trigger mode, the trigger will only fire once. So the ! has an effect but nothing I tried seemed to enable it.
I then tried repeating all of my other tests to see if there was any improvements. Sadly, there were no changes in the speed I could achieve.
dietert1:
Yes, in the description of "!" mode the manual does not mention the serial interface. But it mentions "Fluke Application Bulletin 25". That document should have more details. On ebay i just found "Fluke AB-15", so maybe someone can find "AB-25" for us.
Regards, Dieter
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