Oki OKIFAX 5750 Service Manual page 820

A3.1.1 CPU
Functions
A 32-bit RISC CPU is used as a core and it is provided with the following peripheral functions:
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Built-in PROM/Mask ROM
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Built-in RAM
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Bus state controller (DRAM control and chip select creation)
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Interrupt controller
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DMA controller
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16-bit timer pulse unit
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Serial communication interface
(1) CPU's throughput
The basic clock frequency is 20 MHz. A program/data is stored in the built-in ROM/RAM. The rated throughput is 20 MIPS when optimum object code has been
created. However, the actual throughput is reduced due to the access times needed by external devices.
(2) Built-in PROM/Mask ROM
The built-in ROM size is 64 KB and memory addresses range from 000000h to 000FFFh.
(3) Built-in RAM
The built-in RAM size is 4 KB and memory addresses range from FFFF000h to FFFFFFFh.
(4) Bus state controller
The bus state controller controls the DRAM and accesses the flash ROM and external devices. (Figure 6.1 shows the timing chart of the basic bus cycle.)
(5) Interrupt controller
This system has nine interrupts. Three interrupts /IRQ 4, /IRQ6, and /IRQ7 are used but the other six interrupts /IRQ0 to /IRQ3, IRQ5, and NMI are not used.
Interrupts are allocated as follows:
/IRQ7 = Print-related user timer interrupt
/IRQ6 = Matsushita V.34 modem interrupts 1 and 2, Sanyo V.17 modem, encryption, line ringing tone (Ring), Sanyo read control IC
Service Guide OKIFAX 5750/5950
Chapter A Board Descriptions
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