my LPC122x gives me an interrupt on UART0 with IIR - INTID (bit 3:1) containing the value 0x0. The UM10441 states this is a modem interrupt. But the UM gives no further info on this interrupt and the next page even states the value "0000" is reserved. So in the end I am confused what caused the interrupt and how to stop it (not knowing why is never good and it's also a minor performance issue).
MCR and MSR register are 0x00 so Modem is not used at all...
P.S. just found a "Modem status interrupt generation" Table in the doc naming an "enable modem status interrupt" flag "ER" but no link or info as there seems to be no ER register around. Maybe IER but that is used as IER just in the next coulum so I doubt it. IER is marked as reserved so it might at least match as it is not anything else...but even if: the value if IER is 0x05 for me so not set -> should be no problem