ML51Dec. 05, 2018 Page 361 of 401 Rev 1.00ML51 SERIES TECHNICAL REFERENCE MANUAL30 POWER MONITORINGTo prevent incorrect execution during power up and power drop, The ML51 provide three powermonitor functions, power-on detection and brown-out detection.30.1 Power-On DetectionThe power-on detection function is designed for detecting power up after power voltage reaches to alevel where system can work. After power-on detected, the POF (PCON.4) will be set 1 to indicate acold reset, a power-on reset complete. The POF flag can be cleared via software.PCON – Power Control7 6 5 4 3 2 1 0SMOD SMOD0 LPR POF GF1 GF0 PD IDLR/W R/W RW R/W R/W R/W R/W R/WAddress: 87H, All pagess POR reset value: 0001 000b, other reset value: 000U 0000bBit Name Description4 POF Power-on reset flagThis bit will be set as 1 after a power-on reset. It indicates a cold reset, a power-on reset complete.This bit remains its value after any other resets. This flag is recommended to be cleared viasoftware.30.2 Brown-Out Detection (BOD)The other power monitoring function brown-out detection (BOD) circuit is used for monitoring the VDDlevel during execution. There are eight CONFIG selectable brown-out trigger levels available for widevoltage applications. These eight nominal levels are 1.8V, 2.0V, 2.4V, 2.7V, 3.0V, 3.7V and 4.4Vselected via setting CBOV[2:0] (CONFIG2[6:4]). BOD level can also be changed by setting BOV[2:0](BODCON0[6:4]) after power-on. When VDD drops to the selected brown-out trigger level (VBOD), theBOD logic will either reset the MCU or request a brown-out interrupt. User may decide to being resetor generating a brown-out interrupt according to different applications. VBOD also can be set bysoftware after power-on. Note that BOD output is not available until 2~3 LIRC clocks after softwareenabling.The BOD will request the interrupt while VDD drops below VBOD while BORST (BODCON0.2) is 0. Inthis case, BOF (BODCON0.3) will be set as 1. After user cleared this flag whereas VDD remains belowVBOD, BOF will not set again. BOF just acknowledge user a power drop occurs. The BOF will also beset as 1 after VDD goes higher than VBOD to indicate a power resuming. The BOD circuit provides anuseful status indicator BOS (BODCON0.0), which is helpful to tell a brown-out event or powerresuming event occurrence. If the BORST bit is set as 1, this will enable brown-out reset function.
