hi I work by LPC2138/01, and i config I/O ports as fast I/O(SCS=0x3). i change I/O pin in simulation exactly, also I/O pins change whitout any problem in run mode. but i cannot change I/O pin in debugging mode, even when i click a bit on PINxDIR register manually, it unchecked after a short time. I use Keil V4.6.00. How can I solve my problem by fast I/O pin in debug mode???
i debug my hardware by J-LINK debugger. my LED is active low. when bebugger is stopped and SCS=0, if i click on IO1DIR bits (peripheral -> GPIO 1 - slow interface) portpin config becomes as output and my LED becomes on. but when SCS=0x3, if i click on FIO1DIR bits (peripheral -> GPIO 1 - fast interface) again portpin config becomes as output and my LED becomes ON, after short time(0.5s) automatically "FIO1DIR bit tick" is removed, and portpin config becomes as input again. This situation just occurs for all bit in fast GPIO registers(FIOxMASK, FIOxSET for PORT0 and PORT1) Why? i don't know!!!