eZ80L92 MCU
Product Specification
45
{MBASE[7:0], I[7:0], 1Eh} and {MBASE, I[7:0], 1Fh}. The least significant byte is
stored at the lower address.
When any one or more of the interrupt requests (IRQs) become active, an interrupt request
is generated by the interrupt controller and sent to the CPU. The corresponding 8-bit
interrupt vector for the highest priority interrupt is placed on the 8-bit interrupt vector bus,
IVECT[7:0]. The interrupt vector bus is internal to the ZLP12840 and is therefore not
visible externally. The response time of the eZ80 CPU to an interrupt request is a
function of the current instruction being executed as well as the number of WAIT states
being asserted.
The interrupt vector, {I[7:0], IVECT[7:0]}, is visible on the address bus, ADDR[15:0],
when the interrupt service routine begins. The response of the eZ80 CPU to a vectored
interrupt on the ZLP12840 is explained in Table 12. Interrupt sources are required to be
active until the Interrupt Service Routine (ISR) starts. We recommend you to change the
Interrupt Page Address Register (I) value from its default value of 00h as this address can
create conflicts between the non-maskable interrupt vector, the RST instruction addresses,
and the maskable interrupt vectors.
Table 12. Vectored Interrupt Operation
Memory
Mode
ADL MADL
Bit
Bit Operation
Z80 Mode
0
0
Read the LSB of the interrupt vector placed on the internal vectored
interrupt bus, IVECT [7:0], 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] on the ({MBASE,SPS}) stack.
The ADL mode bit remains cleared to 0.
The interrupt vector address is located at { MBASE, I[7:0], IVECT[7:0] }.
PC[15:0] ← ( { MBASE, I[7:0], IVECT[7:0] } ).
The ending Program Counter is effectively {MBASE, PC[15:0]}
The interrupt service routine must end with RETI.
PS013015-0316
Interrupt Controller
ZILOG [ ZILOG, INC. ]
