Lpc2000

--- In lpc2000@yahoogroups.com, "Sagaert Johan" <sagaert.j@...> 
wrote: 
 
> I am a bit confused : some evaluation boards use a pull-up 
(olimex) some 
> other (mcb2103 ) use a pull-down resistor on the RTCK pin. 
>  
> Whats the correct one ? 
 
Depends on what you want to do with the board and how your debugger 
handles RTCK during pulling reset: 
 
RTCK is P1.26, which according to UM10120 (this is for Lpc213x) 
chapter 7.4.3 p.78 determines the usage of P1.26..P1.31: either JTAG 
pins or GPIO. A pulldown makes these guys debugger pins, while a 
pullup makes them (initially) GPIOs. 
 
Now if your debug cable overrides the pullup while operating the 
reset, all is well. If it doesn't you have to put a a pulldown 
otherwise you cannot do JTAG debugging. So a pulldown is a safe bet, 
while a pullup is advantageous, if you don't want to waste power 
(internal pullup and external pulldown) in deep sleep mode. 
 
Gunter