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BS-2 READ timing — Parallax Forums

BS-2 READ timing

tomcrawfordtomcrawford Posts: 1,129
in BASIC Stamp
I have recently done some experiments that suggest the BS-2 READ statement takes roughly 1 msec per byte. (Don't ask why). This seems to be VERY ssslllllooooww.

Can anyone confirm or deny?

Thanks for your kind attention.

Tom Crawford

Comments

  • DigitalBobDigitalBob Posts: 1,515
    I wonder if I loaded in hex to a blank PIC16F, if the timing would be slow
  • JonnyMacJonnyMac Posts: 9,211
    The only way to confirm is with a 'scope. I did a project a long time ago with a BS2 that needed a 100ms loop time, regardless of the path taken through the loop. I used a spare pin and a TOGGLE instruction to flip its state each time through, using a 'scope to measure. It took a couple days to pad the code, but I got as near to 100ms through the loop, no matter the program state.
  • DigitalBobDigitalBob Posts: 1,515
    This is my PIC16Fxxx hex, set Porta to output, turn on portA

    :020000000328D3
    :0E000600831603138501FF308312850009283D
    :04400E00F22F000786
    :00000001FF

    You add turn off and clock it with your scope, on, off, on, off etc.
  • tomcrawfordtomcrawford Posts: 1,129
    I had used a scope and I guess it is what it is. Just couldn't believe it. Even the BS-2pe, takes 100s of usec to do a GET.
  • DigitalBobDigitalBob Posts: 1,515
    This is the PIC16F57 instruction cycle timing.
    pdf
    pdf
    PIC16F57 Instruction cycle.pdf
    338K
  • Tracy AllenTracy Allen Posts: 6,666
    edited 2020-12-08 00:38
    I did similar tests back some time ago.
    http://emesystems.com/OLDSITE/BS2speed.htm
    What I have written there for a READ 0,x command on the BS2 is 550µs.
    Both GET and PUT took a little more than 200µs each, and, not surprisingly, WRITE came in at 6000µs and depended more on the eeprom.
    I don't know why READ took that long, but it does require several eeprom accesses coming and going.

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