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Chapter 2 CPU Basics
Bus Interface
2-3 Bus Interface
2-3-1 Bus Controller
The MN101C series provides separate buses to the internal memory and internal peripheral circuits to
reduce bus line loads and thus realize faster operation.
There are three such buses: ROM bus, RAM bus, and peripheral expansion bus (I/O bus). They connect
to the internal ROM, internal RAM, and internal peripheral circuits respectively. The bus control block
controls the parallel operation of instruction read and data access. A functional block diagram of the bus
controller is given below.
Figure 2-3-1 Functional Block Diagram of the Bus Controller
Instruction
queue
Program address Operand address
Interrupt
control
Interrupt
bus
Memory control register
Memory mode setting
Bus access (wait)
control
Bus
arbitor
Peripheral
extension bus
Internal
peripheral functions
RAM bus
Internal RAM
ROM bus
AD
AD
AD
Address decode
Bus controller
Internal ROM