ST63140 datasheet(25/86 Pages) STMICROELECTRONICS

25 / 86 page

MCU Initialization Sequence

When a reset occurs the stack is reset to the pro-

gram counter, the PC is loaded with the address of

the reset vector (located in the program ROM at

addresses FFEh & FFFh). A jump instruction to the

beginning of the program has to be written into

these locations. After a reset a NMI is automat-

ically activated so that the core is in non-maskable

interrupt mode to prevent false or ghost interrupts

during the restart phase. Therefore the restart rou-

tine should be terminated by a RETI instruction to

switch to normal mode and enable interrupts. If no

pending interrupt is present at the end of the reset

routine the ST631xx will continue with the instruc-

tion after the RETI; otherwise the pending interrupt

will be serviced.

RESET

IS RESET

STILL PRESENT ?

YES

VA000427

NMI MASK SET

INT LATCH CLEARED

( IF PRESENT )

SELECT

NMI MODE FLAGS

PUT FFEh

ON ADDRESS BUS

LOAD PC

FROM RESET LOCATIONS

FFE / FFF

FETCH INSTRUCTION

Figure 21. Reset & Interrupt Processing

Flow-Chart

RESET VECTOR

INITIALIZATION

ROUTINE

JP: 2 BYTES/4 CYCLES

RETI: 1BYTES/2 CYCLES

RETI

VA 000181

RESET

Figure 22. Restart Initialization Program

Flow-Chart

RESET (Continued)

ST63140,142,126,156

21/82

ST63140 数据表(PDF) 25 Page - STMicroelectronics

ST63140 数据表(HTML) 25 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

数据表下载