HD404654 Datasheet, PDF (16/111 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404654 Series
A block diagram of the interrupt control circuit is shown in figure 8, interrupt priorities and vector
addresses are listed in table 2, and interrupt processing conditions for the 11 interrupt sources are listed in
table 3.
An interrupt request occurs when the IF is set to 1 and the IM is set to 0. If the IE is 1 at that point, the
interrupt is processed. A priority programmable logic array (PLA) generates the vector address assigned to
that interrupt source.
The interrupt processing sequence is shown in figure 9 and an interrupt processing flowchart is shown in
figure 10. After an interrupt is acknowledged, the previous instruction is completed in the first cycle. The
IE is reset in the second cycle, the carry, status, and program counter values are pushed onto the stack
during the second and third cycles, and the program jumps to the vector address to execute the instruction
in the third cycle.
Program the JMPL instruction at each vector address, to branch the program to the start address of the
interrupt program, and reset the IF by a software instruction within the interrupt program.
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