OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE

Interrupt Enable Bit (IE) = 1

Trap Flag (TF) = 1

NMI

Divide

Timer Interrupt

Push PSW, CS, IP

Fetch Divide Error Vector

Push PSW, CS, IP

Fetch NMI Vector

Interrupt Enable Bit (IE) = 0 Trap Flag (TF) = 0

Interrupt Enable Bit (IE) = 0 Trap Flag (TF) = 0

Push PSW, CS, IP

Fetch Single Step Vector

Execute Single Step

Service Routine

IRET

Interrupt Enable Bit (IE) = 0

Trap Flag (TF) = ???

Interrupt Enable Bit (IE) = 1

Trap Flag (TF) = X

Interrupt Enable Bit (IE) = 0 Trap Flag (TF) = 0

Push PSW, CS, IP

Fetch Single Step Vector

Interrupt Enable Bit (IE) = 1 Trap Flag (TF) = X

Execute Single Step Service Routine

IRET

A1034-0A

Figure 2-30. Simultaneous NMI, Single Step and Maskable Interrupt

2-49

Page 78
Image 78
Intel 80C188XL, 80C186XL Interrupt Enable Bit IE = Trap Flag TF =, Simultaneous NMI, Single Step and Maskable Interrupt