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CHAPTER 3 CPU AND CONTROL UNITS
3.10
Reset (Device Initialization)
This section describes the reset operation that is initialization of the MB91260B series.
When a reset source occurs, the device stops all of the program and hardware
operations and initializes the device status. This initialized state is called the reset
state.
When the reset source is eliminated, the device restarts program and hardware
operations from the initial state. A series of steps taken by the device from the reset
state to the beginning of the restart is called the reset sequence.
■ Reset Levels
The MB91260B series resets itself at either of the two levels which are different in the cause of reset and
the effect of initialization. Each reset level is described below.
●
Setting initialization reset (INIT)
The setting initialization reset (INIT) is the highest level of reset that initializes all settings.
The major settings initialized by the setting initialization reset (INIT) are listed below.
•
Device operation mode (bus mode and external bus width settings)
•
All of the settings concerning the internal clock (clock source selection, PLL control, and divide ratio
settings)
•
All of the settings for the external bus CS0 area
•
All of the settings concerning other pin states
•
All of the sections initialized by the operation initialization reset (RST)
For details on each setting item, see the description of the relevant function.
Note that the setting initialization reset (INIT) must always be performed via the INIT pin immediately
after the power is turned on.
●
Operation initialization reset (RST)
The operation initialization reset (RST) is the normal level of reset that initializes program operation.
The setting initialization reset (INIT) involves the operation initialization reset (RST).
The major settings initialized by the operation initialization reset (RST) are listed below.
•
Program operation
•
CPU and internal bus
•
Register settings for peripheral circuits
•
I/O port settings
•
Device operation mode (bus mode and external bus width settings)
For details on each setting item, see the description of the relevant function.
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