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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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expanded mode circuit
Started by ●December 6, 2004
Reply by ●December 6, 20042004-12-06
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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 Links > To |
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Reply by ●December 6, 20042004-12-06
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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 Links > To --------------------------------- Yahoo! Groups Links To --------------------------------- |
