UPD78320 Datasheet, PDF (31/88 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCONTROLLER

µPD78320, 78322
3. BLOCK FUNCTIONS
3.1 BUS CONTROL UNIT (BCU)
In the BCU, the necessary bus cycle is started according to the physical address obtained by the execution unit (EXU).
If no bus cycle startup request is made from the EXU, a prefetch address is generated and instruction prefetch is carried
out. The prefetched operation code is fetched into the instruction queue.
3.2 EXECUTION UNIT (EXU)
In the EXU, address calculation, arithmetic logical operation and data transfer are controlled by microprograms. A 256-
byte RAM is built in the EXU.
The 256-byte main RAM in the EXU is accessible by the relevant instruction faster than peripheral RAM (384 bytes).
3.3 ROM/RAM
This block consists of a 16K-byte ROM and a 384-byte peripheral RAM. However, the µPD78320 does not incorporate
ROM.
ROM access can be disabled by EA pin.
3.4 INTERRUPT CONTROLLER
Various interrupt requests (NMI, INTP0 to INTP6) generated either externally or from the peripheral hardware are
serviced by the context switch, vectored interrupt or macro service function.
The 3-level interrupt priority is also specified.
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