8-Bit Microcontroller UPD78F0714 Usage Restrictions
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1. detection or it is an interrupt generated when the LVI operation is enabled must be identified with respect to the interrupt service routine Concerning the use as the interrupt function the wPD78F0714 user s manual document number U16928JJ1VOUDO00 U16928EJ1VOUDOO and the actual device differ in the following three points 1 Zero is always read from bit 0 of the interrupt request flag register IFOL 2 Interrupts cannot be masked with bit 0 of the interrupt mask flag register MKOL 3 The interrupt priority order cannot be changed with bit O of the priority flag register PROL The interrupt with the highest priority is always serviced Conditions under which this issue does not occur When the LVI function is not used Workaround Implement any of the following workarounds 1 When using the LVI for generating reset Add an interrupt routine 1 Wait for 0 2 ms or longer using software 2 Wait until after confirming that the power supply voltage Vpop is higher than the detection voltage Vivi using bit O LVIF of the LVIM register 3 Set bit 1 LVIMD of the LVIM register to 1 ZBG CC 07 0014 Attachment 3 3 2 When using the LVI for generating interrupts 1 Define the flag as a global variable 2 Set the flag before enabling the LVI operation The meanings of this flag are as follows 0 It is confirmed that the power supply voltage Vpp is higher than the detection voltage Vivi after the LVI op2. Microcontroller Technical Information Document No ZBG CC 07 0014 Date issued July 18 2007 Issued by 8 Bit Microcontroller PD78F0714 2nd Product Solution Group Multipurpose Microcomputer Systems Division Microcomputer Operations Unit NEC Electronics Corporation Usage Restrictions Related documents Notification V Usage restriction UPD78F0714 User s Manual U16928EJ classification Upgrade Document modification Other notification Affected product uPD78F0714 2 Restriction details A new restriction No 1 has been added e No 1 Restriction on interrupt signals generated by low voltage detector Masking of interrupt sources to be masked is not available and interrupts operate as non maskable interrupts 3 Workaround The following workaround is available for this restriction See the attachment for details e No 1 When using the low voltage detector be sure to include into interrupt servicing a program routine that judges the validity of interrupts generated by the low voltage detector This also applies when interrupts generated by the low voltage detector are used as reset 4 Modification schedule Device modification for restrictions is not planned Regard the restriction added in this document as a usage restriction The descriptions concerning this issue in the user s manual will be corrected in the next revision Chapters in question Chapter 19 Interrupt Functions an
3. d Chapter 23 Low Voltage Detector 5 List of restrictions The restriction history and detailed information is described in the attachment 6 Document revision history 8 Bit Microcontroller PD78F0714 Usage Restrictions Document Number Date Issued ZBG CC 07 0014 latest version July 18 2007 ZBG CC 07 0014 List of Restrictions in PD78F0714 1 Product Version uPD78F0714 Rank K The rank is indicated by the letter appearing as the 5th digit from the left in the lot number marked on each product 2 Product History Usage Restrictions Restriction on interrupt signals generated by low voltage detector EA i O Not applicable A Applicable ZBG CC 07 0014 Attachment 2 3 3 Details of Usage Restrictions No 1 Restriction on interrupt signals generated by low voltage detector Description The following two operating modes are available for the low voltage detector LVI 1 Used as reset 2 Used as interrupts An LVI interrupt may occur when the LVI operation is enabled in both of the above modes In other products interrupts generated by the LVI operate as maskable interrupts and can therefore be masked In this product however they operate as non maskable interrupts and therefore cannot be masked The program of LVI interrupt service routines must therefore be included even if interrupts generated by the LVI are used for reset When they are used as interrupts whether the interrupt is caused by low voltage
4. eration 1 It has not been confirmed that the power supply voltage Vpop is higher than the detection voltage Vivi after the LVI operation Enable the LVI operation gt gt O YS aS Wait for 0 2 ms or longer using software Wait until after confirming that the power supply voltage VoD is higher than the detection voltage VLvi using bit O LVIF of the LVIM register 6 Clear the flag C Add the following processing at the beginning of interrupts 1 Check the flag 0 Normal processing 1 Implement the following steps 2 Wait for 0 2 ms or longer using software 3 Wait until after confirming that the power supply voltage Vpp is higher than the detection voltage Vivi using bit 0 LVIF of the LVIM register Clear the flag T Return to the main routine C Remark In addition to the above code processing to wait for the voltage variation period is required in a system in which the power supply voltage Vpop varies around the LVI detection voltage Contact an NEC Electronics sales representative if you have any questions or concerns regarding this issue
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