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expanded mode circuit

Started by kokhuikang December 6, 2004

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.




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





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


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