hello, i'm recently debuging a system using a am188es-25 chip. the program is working fine except one thing: In the system, 7 external interrupt is used(full nesty mode,all periodical pulse). some of them is periodically enabled and disabled(use imask register 28h). when the interrupt is enabled(interrupt signal is not actived), the interrupt service routine is actived immediately and run only once. it seems that the interrupt signal is latched, regardless the imask register's status.