Page 66 of the 18c452 manual (DS39026B, 7/99) indicates, in the
description of INTCON2,7 that "0= PORTB pull-ups are enabled by
individual port latch values." This SEEMS to indicate that the output
latch, which is not used when the port is in input mode, enables the weak
pull-ups on a pin-by-pin basis. However, looking at page 80, the
description of port B shows no connection betwee the output latch and the
weak pull-up logic. Instead, it appears the pull-ups are enabled only
when the appropiate TRIS bit is high. It'd be interesting if instead of
the pull-up gate being connected to the TRIS latch, it were connected to
the output latch. This would allow individual control of the weak
pull-ups. The fact that the pull-up would still be enabled when the port
is an output would not be a problem since the pull-up would be disabled
when the output was low.
        So... Which is right? Page 66 or page 80? Or, is my datasheet out of
date?

Harold



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