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CHAPTER 7 RESETS
7.3 External Reset Pin
The external reset pin (RST pin) is an input pin used exclusively for a reset. Inputting an
L level signal generates an internal reset. For the MB90360-series, resets are generated
in synchronization with the CPU operating clock. However, initialization of external pin
is asynchronous with the CPU operating clock.
■ Block Diagrams of the External Reset Pin
●
Block diagram of the external reset pin
Figure 7.3-1 Block Diagram of the External Reset Pin
Note:
Inputs to the RST
pin are accepted during cycles in which memory is not affected to prevent memory
from being destroyed by a reset during a write operation.
A clock is required to initialize the internal circuit. In particular, an operation with an external clock
requires clock input together with reset input.
RST
Pch
Nch
Pin
Input buffer
CPU operating clock
(PLL multiplication circuit,
2-frequency division of HCLK)
HCLK: Oscillation clock
Synchronization
circuit
CPU
peripheral function
External pin