ZiLOG eZ80

eZ80
®
CPU
User Manual
UM007714-0908 Interrupts
44
In applications that run Z80 mode code exclusively, the interrupt vector address is
{MBASE, I[7:1], IVECT[8:0]}. A 16-bit word is fetched from the interrupt vector address
and loaded into the lower two bytes of the Program Counter, PC[15:0].
In mixed-memory or ADL mode applications, the interrupt vector address is {I[15:1],
IVECT[8:0]}. A 24-bit word is fetched from the interrupt vector address and loaded into
the Program Counter, PC[23:0].
eZ80190, eZ80L92, and eZ80F92/F93 devices only support an 8-bit I register, an 8-bit
IVECT, and a 16-bit word fetch in ADL modes. Refer to the eZ80
®
and eZ80Acclaim!
®
product specifications for information on product specific vectored interrupt modes.
Table 25. Vectored Interrupt Operation
Memory Mode
ADL
Bit
MADL
Bit Operation
Z80 Mode 0 0
Read the LSB of the interrupt vector placed on the internal
vectored interrupt bus, IVECT [8:0], by the interrupting
peripheral.
• IEF1 ← 0
• IEF2 ← 0
• The starting Program Counter is effectively {MBASE,
PC[15:0]}.
• Push the 2-byte return address PC[15:0] onto the
({MBASE,SPS}) stack.
• The ADL mode bit remains cleared to 0.
• The interrupt vector address is located at { MBASE,
I[7:1], IVECT[8:0] }.
• PC[15:0] ← ( { MBASE, I[7:1], IVECT[8:0] } ) .
• The ending Program Counter is effectively {MBASE,
PC[15:0]}
• The interrupt service routine must end with RETI.
ADL Mode 1 0
Read the LSB of the interrupt vector placed on the internal
vectored interrupt bus, IVECT [8:0], by the interrupting
peripheral.
• IEF1 ← 0
• IEF2 ← 0
• The starting Program Counter is PC[23:0].
• Push the 3-byte return address, PC[23:0], onto the SPL
stack.
• The ADL mode bit remains set to 1.
• The interrupt vector address is located at { I[15:1],
IVECT[8:0] }.
• PC[23:0] ← ( { I[15:1], IVECT[8:0] } ) .
• The ending Program Counter is { PC[23:0] }.
• The interrupt service routine must end with RETI.
Note: