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8-4
CIRCUIT DESCRIPTION
2. Circuit operation
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1 CPU circuit
• Power supply
The power supply toward the CPU (IC7002) is produced by the regulator.
Power supply (+3.3V) for CPU I/O pin: Produced from Standby +5V by IC7005.
Power supply (+1.2V) for CPU core: Produced from Standby +3.3V by IC7004.
• Reset
IC7000 is a circuit to control power voltage supervision and resetting. This circuit is used to supervise
Standby +3.3V that is the basis for the power supply of the CPU core. The CPU is reset if this voltage
becomes lower than +3.0V.
D7001 is unlit when the reset output is generated from IC7000. D7001 is lit when the reset condition is
canceled.
•Clock
X7001 is an oscillator of 12MHz. Based on this 12MHz, the CPU generates various clock signals in con-
junction with the PLL in the CPU. These signals are the main clock to be used inside the CPU, the bus
clock to access the peripheral devices, and so on.
• Program/Data memory
The firmware for CPU operation and the associated data are accommodated in the Flash ROM of IC7007
and IC7008. The respective ROM functions are specified below.
IC7007 : Storage area for BIOS and various data
IC7008 : Storage area for firmware
When the reset condition is canceled by IC7000 after the power supply has been turned ON, the CPU
firstly reads out the BIOS data of IC7007. It then starts up itself based on these data. After that, it reads out
the firmware data of IC7008. It operates while referring to the data of IC7007.
The adjusting values and such data are written in IC7007 for storage.
The serial number of the unit and information about the usage time are stored in the EEPROM of IC7003.
• Work memory
IC7006 is an SDRAM. It is used as a work area while the CPU is in operation.
The circuits between the CPU and the SDRAM are operated in synchronization with the bus clock of
133MHz.
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