Post by thread:PIC16C84 and RA4

Hello, I was trying to use PORTA<4> as output pin but did not have any luck. Even if I use something like that: BSF PORTA,4 LOOP: GOTO LOOP I do not see any positive voltage on output pin. Could it be related to the fact that RA4 is a schmit trigger ??? Thank you. -Alex. PS. All PORTA pins configured as output.

A quick look at my databook shows that RA4 is an open drain output pin. This means that the pin must have an external pullup resistor to function as an output. Please try adding a 4700 ohm resistor between the RA4 pin and 5 volts, that should fix it. --- Steve {Quote hidden}>Hello, >I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? >Thank you. >-Alex. >PS. All PORTA pins configured as output.

Hi Alex, > I was trying to use PORTA<4> as output pin but did not have any > luck. Even if I use something like that: > BSF PORTA,4 > LOOP: GOTO LOOP > > I do not see any positive voltage on output pin. > Could it be related to the fact that RA4 is a schmit trigger ??? > > PS. All PORTA pins configured as output. The PORTA<4> pin is open collector, it only has 'drive' to 0V and you have to externally pull the output up to 5V with a suitable resistor 1k to 10k is usually safe. Otherwise your coding looks fine. Cheers -- Kalle Pihlajasaari spam_OUTkalleTakeThisOuTdata.co.za Interface Products Box 15775, Doornfontein, 2028, South Africa +27 (11) 402-7750 Fax: +27 (11) 402-7751

Alexey Zaparovanny <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> wrote: > I was trying to use PORTA<4> as output pin but did not have any > luck. Even if I use something like that: > BSF PORTA,4 > LOOP: GOTO LOOP > > I do not see any positive voltage on output pin. > Could it be related to the fact that RA4 is a schmit trigger ??? > > PS. All PORTA pins configured as output. Alexey: PORTA<4> is an open-collector output; you need a pullup resistor. -Andy Andrew Warren - fastfwdKILLspamix.netcom.com Fast Forward Engineering, Vista, California http://www.geocities.com/SiliconValley/2499

> > Hello, > I was trying to use PORTA<4> as output pin but did not have any > luck. Even if I use something like that: > BSF PORTA,4 > LOOP: GOTO LOOP > > I do not see any positive voltage on output pin. > Could it be related to the fact that RA4 is a schmit trigger ??? > Actually, RA4 is also an open-collector output, so you will *never* see any positive voltage on it without a pull up resistor... Larry Battraw (.....larryKILLspam.....cicdphx.com)

Alex wrote... >Hello, >I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP > >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? > No. It's because RA4 is actually an Open Collector Output, which means that it can only pull a bus (as opposed to a line) to ground. Think of it as a switch pulling a signal to ground. If you want to use it as a driver, put a pull-up on it and it will work like the other ports. Myke >Thank you. > >-Alex. > >PS. All PORTA pins configured as output. > > Do you ever feel like an XT Clone caught in the Pentium Pro Zone?

>I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? > >Thank you. RA4 on the '84 is open drain when configured as an output. Try using a pull up resistor of 10K or so. Regards Tony Just when I thought I knew it all, I learned that I didn't.

At 01:57 PM 10/8/96 -0400, you wrote: >Hello, >I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP > >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? > >Thank you. > >-Alex. > >PS. All PORTA pins configured as output. > Hi Alex. The problem is because PORTA<4> is open-collector. This pin can only drive to LOW. To put this pin on HIGH, you must put one pull-up resistor to VCC. I hope this help. ********************************************* Marcus A. de Souza EraseMEmarcusspam_OUTTakeThisOuTunetsul.com.br Handicom Eletronica - Florianopolis SC Brazil *********************************************

At 01:57 PM 8/10/96 -0400, you wrote: Alex, This output is an open collector type. {Quote hidden}>Hello, >I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP > >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? > >Thank you. > >-Alex. > >PS. All PORTA pins configured as output. > > Peter Grey Australia

Myke wrote >No. It's because RA4 is actually an Open Collector Output, which means that >it can only pull a bus (as opposed to a line) to ground. >Think of it as a switch pulling a signal to ground. >If you want to use it as a driver, put a pull-up on it and it will work like >the other ports. This is not exactly true as this port cannot source any current to a device, such as driving a led. It can only sink current and thus works as an inverting driver, as you would have to take the output low to light the LED from a positive rail. Tony Just when I thought I knew it all, I learned that I didn't.

Hi here SET from Argentina: Sorry if this is allready answered but the mails come here with some delay: >Hello, >I was trying to use PORTA<4> as output pin but did not have any >luck. Even if I use something like that: > BSF PORTA,4 >LOOP: GOTO LOOP >I do not see any positive voltage on output pin. >Could it be related to the fact that RA4 is a schmit trigger ??? Alex: PORTA,4 is open collector, put a pull-up resistor suitable for your case (20K is the value used by Mchip as weak pull-up in port B INs (not outs) that's more than enough to get it working, but if you plan to handle a transistor you will need a lower resistor). bye SET ******************************************************************************** Salvador Eduardo Tropea (SET) - salvadorspam_OUTinti.edu.ar Work: INTI (National Institute of Industrial Technology) Sector: ICE (Electronic Control & Instrumentation) Post (Home): Curapaligue 2124 - Caseros (1678)- Buenos Aires - Argentina

Tuesday October 08 1996 14:57, @spam@azaparovKILLspamCYBERCOM.NET wrote to Alex Torres: a> a> Hello, a> I was trying to use PORTA<4> as output pin but did not have a> any luck. Even if I use something like that: a> BSF PORTA,4 a> LOOP: GOTO LOOP Are You set it's bit in TRISA register before ? a> PS. All PORTA pins configured as output. You are sure ? And next: PA4 have an open collector output! Are you use pull-up resistor (~10k) from PA4 to Vdd ? Best Wishes, Alex Torres. Kharkov, Ukraine, exUSSR. E-Mail To : KILLspamaltorKILLspamcook.kharkov.ua via InterNet or 2:461/28 via FidoNet --- GoldED 2.50.A0531+ * Origin: Future Hardware, (0572)32-31-62 (2:461/28)