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Discussion Groups | M68HC11 | expanded mode circuit
Technical discussions about Freescale Microcontrollers: M68HC11. (Freescale Semiconductor is a Subsidiary of Motorola).
expanded mode circuit - kokhuikang - Dec 6 0:52:00 2004
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hi, is there anyone here have the circuit of expanded mode? The circuit must consists of one 74LS138 decoder and one latch output that i will be using to control my stepper motor.Thanks. |
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Re: expanded mode circuit - Author Unknown - Dec 6 2:04:00 2004
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There is good information on expanded mode in the 68HC11 Reference Manual. http://www.freescale.com/files/microcontrollers/ doc/ref_manual/M68HC11RM.pdf For many 68HC11 variations, you can use port pins to drive your stepper motors without an external latch. Expanded mode is most often used to add external memory. If you need additional external outputs, you might want to consider using the SPI bus to drive a serial to parallel shift register, such as the 74HC595. Hope this is helpful. Kerry Berland > > hi, is there anyone here have the circuit of expanded mode? The > circuit must consists of one 74LS138 decoder and one latch output > that i will be using to control my stepper motor.Thanks. > > > Yahoo! Groups Sponsor ADVERTISEMENT > > Yahoo! Groups Links > To |
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Re: expanded mode circuit - bart homerson - Dec 6 17:41:00 2004
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I would have to agree here. I too needed to go from serial to parallel in a circuit
of mine. I had considered the 138 chip, but upon further experimentation, I found that the
chip simply did not work as I would have liked. You see, with the 138 only one of the
8-pins can be at a low state at any given time--I think I have this right, but look over
the truth chart of this chip and you will see what I am talking about. The 595 worked
wonders for me because I was able to make any, or all, of the pins whichever state that I
needed; they even work well cascaded. If you can, shy away from the 138 unless you just
need one of the 8 pins to change state; if that is the case, then the 138 is for you.
Just my two cents... LF wrote: There is good information on expanded mode in the 68HC11 Reference Manual. http://www.freescale.com/files/microcontrollers/ doc/ref_manual/M68HC11RM.pdf For many 68HC11 variations, you can use port pins to drive your stepper motors without an external latch. Expanded mode is most often used to add external memory. If you need additional external outputs, you might want to consider using the SPI bus to drive a serial to parallel shift register, such as the 74HC595. Hope this is helpful. Kerry Berland > > hi, is there anyone here have the circuit of expanded mode? The > circuit must consists of one 74LS138 decoder and one latch output > that i will be using to control my stepper motor.Thanks. > > > Yahoo! Groups Sponsor ADVERTISEMENT > > Yahoo! Groups Links > To Yahoo! Groups SponsorADVERTISEMENT --------------------------------- Yahoo! Groups Links To --------------------------------- |
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