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Discussion Groups | 68HC12 | How to increase drive capabitity of DP256 IO ports
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
How to increase drive capabitity of DP256 IO ports - linktek - Sep 19 8:35:00 2003
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Hi, I need to increase the drive capacity from the meager 2.5mA per IO pin to about 20mA per IO pin for 8 IO lines. Now the trick is to retain the bi-direction function of the IO pins. How can I increase the the output drive of the DP256 IO pins without loosing input capabitity with a solution that will fit on a dime? Frank [Non-text portions of this message have been removed] |
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Re: How to increase drive capabitity of DP256 IO ports - ra - Sep 19 9:06:00 2003
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The "Electrical Characteristics" of the DP256 manual say that the IO pins already have max 25 mA current, so maybe you don't need to do anything?! On Freitag, Sep 19, 2003, at 15:35 Europe/Paris, linktek wrote: > Hi, > > I need to increase the drive capacity from the meager 2.5mA per IO pin > to > about 20mA per IO pin for 8 IO lines. Now the > trick is to retain the bi-direction function of the IO pins. How can I > increase the the output drive of the DP256 IO pins without > loosing input capabitity with a solution that will fit on a dime? > > Frank > > [Non-text portions of this message have been removed] > ------------------------ Yahoo! Groups Sponsor > ---------------------~--> > Upgrade to 128-Bit SSL Security! > http://us.click.yahoo.com/p7cEmB/s7qGAA/yigFAA/dN_tlB/TM > --------------------------------------------------------------------- > ~-> > > -------------------------------------------------------- > To unsubscribe from this group, send an email to: > To learn more about Motorola Microcontrollers, please visit > http://www.motorola.com/mcu |
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Re: How to increase drive capabitity of DP256 IO ports - Doron Fael - Sep 19 10:38:00 2003
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Frank, The recommended operating conditions of the DP256 allow sourcing or sinking 10mA per normal I/O pin, when the I/O is configured for full-drive. In reduced drive, the I/O can sink or source 2mA. (the absolute maximum rating specify 25mA - but it is not recommended to operate the I/O in this current) If you can use another HCS12 derivative, the 9S12H256 and H128 have 24 I/O line (Ports U, V, and W) with increased I/O drive - allowing 20mA for both sink and source currents. An option to increase the drive and maintain the input capability involves 2 i/o pins per generated higher current pin: You can use a 74ACT126 and a 74ACT125 (that allow 24mA source and sink current) connected as follows: A) The input of the 126 and the output of the 125 are connected to the DP256 I/O pin which serves as the input/output I/O. B) The output of the 126 and the input of the 125 are connected together to form your higher current input/output signal. C) A second I/O from the DP256 is connected to the control input of both the 126 and 125, to control the data flow direction. Note the 126 and 125 have opposite active control (126 is active when control is high, and 125 is active when control is low). Thus when the DP256 control pin will be high the direction for the generated high-current i/o is output, and when the DP256 control pin will be low the direction for the generated high-current i/o is input. Hope this helps, Doron Nohau Corporation HC12 In-Circuit Emulators www.nohau.com/emul12pc.html At 04:06 PM 9/19/2003 +0200, you wrote: >The "Electrical Characteristics" of the DP256 manual say that the IO >pins already have max 25 mA current, so maybe you don't need to do >anything?! > >On Freitag, Sep 19, 2003, at 15:35 Europe/Paris, linktek wrote: > > Hi, > > > > I need to increase the drive capacity from the meager 2.5mA per IO pin > > to > > about 20mA per IO pin for 8 IO lines. Now the > > trick is to retain the bi-direction function of the IO pins. How can I > > increase the the output drive of the DP256 IO pins without > > loosing input capabitity with a solution that will fit on a dime? > > > > > > > > Frank [Non-text portions of this message have been removed] |
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