Initial Reset; Pins For Initial Reset; Cold Start And Hot Start - Epson S1C33210 Technical Manual

II-3 INITIAL RESET

Pins for Initial Reset

Table 3.1 shows the pins used for initial reset.
Pin name I/O
#RESET I Initial reset input pin (Low active)
Low: Resets the CPU.
#MNI I NMI request input pin
This pin is also used for selecting a reset method.
High: Cold start
Low: Hot start
The chip is reset when the #RESET pin goes low and starts operating at the rising edge of the reset signal. The CPU
and internal peripheral circuits are initialized while the #RESET pin is low.

Cold Start and Hot Start

The CPU supports two initial reset methods: cold start and hot start. The #MNI pin is used with the #RESET pin to
set this condition.
The differences between cold start and hot start are shown in Table 3.2.
Setup contents
Reset condition
CPU: PC
CPU: PSR
CPU: Other registers
CPU: Operating clock
External bus status (0x48120–0x4813F)
Oscillation circuit
I/O pin status (0x402C0–0x402DF)
Other peripheral circuit
Since cold start initializes all the internal peripheral circuits as well as the CPU, it is useful as a power-on reset.
Hot start initializes the CPU and peripheral circuits, but does not reset the bus control unit and the input, output and
I/O port status. It is therefore useful as a reset that maintains the external bus and I/O pin status during operation.
The #NMI pin that specifies the reset method should be set following the timing chart shown in Figure 3.1.
Cold start is generated
#NMI
#RESET
#NMI must be set to high longer than
the reset pulse width.
(1) Cold start
S1C33210 FUNCTION PART
Table 3.1 Pins for Initial Reset
Table 3.2 Differences between Cold Start and Hot Start
#RESET = low & #MNI = high
(#RESET = low & #NMI = high)
Figure 3.1 Setup of #RESET and #NMI Pins
Function
Cold start
The vector at the boot address is loaded to the PC.
All the PSR bits are reset to 0.
Undefined
The CPU operates with the OSC3 clock.
Initialized
Both the OSC1 and OSC3 circuits start oscillating.
Initialized
Initialized or undefined
Hot start is generated
#NMI
#RESET
#NMI must be set to low longer than
the reset pulse width.
(2) Hot start
EPSON
II CORE BLOCK: INITIAL RESET
Hot start
#RESET = low & #MNI = low
Status is retained.
Status is retained.
(#RESET = low & #NMI = low)
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