8-bit MicrocontrollersのトピックRe: 9S08JM Pullup with External TPMCLK

9S08JM Pullup with External TPMCLK

dp — Fri, 21 Mar 2008 00:24:54 GMT

I am using the IRQ/TPMCLK pin for an external clock input to TPM2 (TPM2SC = 0x18). It appears this combination disables the internal pullup but I cannot find confirmation in the documentation. I have tried setting IRQSC_IRQPE=1 but it has no effect.

I can add an external pullup (this is a prototype) but I'd like to be sure I'm not missing something. Can anyone confirm this behavior or suggest how to enable the internal pullup with this configuration? Thanks.

Dave

P.S.
The external clock source comes though a blocking diode. That's why I need the pullup.

Re: 9S08JM Pullup with External TPMCLK

fabio — Fri, 21 Mar 2008 05:29:01 GMT

Hi dp,

I believe that the pulling device is only available when the IRQ function is active (IRQSC:IRQPE=1). There is no other way to enable pulling devices when this pin is operating as TPMCLK input (as it is not mapped to any PTxPE bit).

Best regards,

Re: 9S08JM Pullup with External TPMCLK

JimDon — Fri, 21 Mar 2008 06:31:57 GMT

The spec says:
"The IRQ pin, when enabled, defaults to use an internal pull device (IRQPDD = 0), the device is a pullup
or pull-down depending on the polarity chosen"

So if it disabled, then the pull up is not connected.

Also note that this in not a pin that is shared with a GPIO, pins that are shared with a GPIO usually can use the pull up/pull downs. If you look at the block diagram, you will see signals coming in thru a port. Generally these signal are buffer by the port. This is not one of these signals.