ST62T08C Datasheet, PDF (20/70 Pages) STMicroelectronics – 8-BIT OTP/EPROM MCUs WITH A/D CONVERTER, OSCILLATOR SAFEGUARD, SAFE RESET AND 20 PINS

ST62T08C/T09C ST62T10C/T20C/E20C
RESETS (Cont’d)
3.2.6 MCU Initialization Sequence
When a reset occurs the stack is reset, the PC is
loaded with the address of the Reset Vector (locat-
ed in program ROM starting at address 0FFEh). A
jump to the beginning of the user program must be
coded at this address. Following a Reset, the In-
terrupt flag is automatically set, so that the CPU is
in Non Maskable Interrupt mode; this prevents the
initialisation routine from being interrupted. The in-
itialisation routine should therefore be terminated
by a RETI instruction, in order to revert to normal
mode and enable interrupts. If no pending interrupt
is present at the end of the initialisation routine, the
MCU will continue by processing the instruction
immediately following the RETI instruction. If, how-
ever, a pending interrupt is present, it will be serv-
iced.
Figure 15. Reset and Interrupt Processing
RESET
RESET
VECTOR
JP
JP:2 BYTES/4 CYCLES
INITIALIZATION
ROUTINE
RETI
RETI: 1 BYTE/2 CYCLES
VA00181
Figure 16. Reset Block Diagram
V_DD
f_OSC
CK
RESET
R_PU
R_ESD1)
POWER ON RESET
WATCHDOG RESET
LVD RESET
AND. Wired
COUNTER
RESET _RESET
1) Resistive ESD protection. Value not guaranteed.
ST6
INTERNAL
RESET
VR02107A
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