Rainbow-electronics ATmega8515L Instrukcja Użytkownika Pobierz pdf (Strona 54)

ATmega8515(L)

2512A–AVR–04/02

Moving Interrupts between

Application and Boot Space

The GeneralInterrupt Control Registercontrols the placement of the InterruptVector

table.

General Interrupt Control

• Bit 1 – IVSEL: Interrupt Vector Select

When the IVSEL bit iscleared(zero), the InterruptVectors are placed at the startof the

Flash memory. When thisbit isset (one), the InterruptVectors aremoved to the begin-

ning of the Boot Loadersection of the Flash.Theactual address of the startof the Boot

Flash section isdeterminedbythe BOOTSZ Fuses.Refer to the section “Boot Loader

Support–Read-While-Write Self-Programming” on page 162 fordetails.Toavoid unin-

tentionalchanges ofInterruptVector tables, a specialwrite proceduremust be followed

to change the IVSEL bit:

1. Write the InterruptVectorChange Enable (IVCE) bit to one.

2. Within four cycles, write the desired value to IVSEL while writing a zerotoIVCE.

Interruptswill automatically be disabledwhilethissequenceis executed. Interrupts are

disabled in the cycle IVCE isset, and theyremain disabled until after theinstruction fol-

lowing the write to IVSEL. If IVSEL is not written, interruptsremain disabledforfour

cycles.The I-bit in the Status Register is unaffectedbythe automaticdisabling.

Note:IfInterruptVectors are placed in the Boot Loadersection andBoot Lock bit BLB02 ispro-

grammed, interrupts are disabledwhileexecuting from theApplication section. If

InterruptVectors are placed in theApplication section andBoot Lock bit BLB12 ispro-

gramed, interrupts are disabledwhileexecuting from the Boot Loadersection. Refer to

the section “Boot LoaderSupport–Read-While-Write Self-Programming” on page 162

fordetails on Boot Lock bits.

Bit 76543 210

INT1 INT0 INT2 – – – IVSEL IVCE GICR

Read/Write R/W R/W R/W RRRR/W R/W

Initial Value00000000

1 2 ... 49 50 51 52 53 54 55 56 57 58 59 ... 222 223

Brak uwag

Rainbow-electronics ATmega8515L Instrukcja Użytkownika Strona 54