Maxim-integrated MAXQ622 Bedienungsanleitung PDF herunterladen (Seite 25)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 2-21

Figure 2-8 shows the code memory with passwords and the location of the values that are programmed into the ULDR/

UAPP registers.

The user loader starting page address is located at 0Fh, one word before the system password. The user application

starting page address is stored one word before the user loader password (i.e., ULDR*Flash page size + 0Fh).

The startup sequence is as follows:

1) The system resets at 8000h and starts running utility ROM code. On a 64KB part with flash pages of 512 bytes,

ULDR and UAPP are at their reset values of 80h (end of flash memory). The PRIV register is at its reset value of

high. The MPE (memory protection enable bit) is at its reset value of 1 (enable).

2) Utility ROM initialization code checks the system password and disables MPE if the password is empty.

3) After utility ROM initialization is complete, the utility ROM passes execution to system code memory at address

0000h.

4) System code starts executing and uses a CP of 0Fh to read the user loader starting page address and writes it into

the ULDR register.

5) After system initialization is complete, system code jumps to address ULDR*Flash page size + 0000h. This jump

automatically drops PRIV to medium.

6) The user-loader code starts executing and uses a CP of ULDR*Flash page size + 0Fh to read the user application

starting page address and writes it into the UAPP register.

7) After user loader initialization is complete, user-loader code jumps to address UAPP*Flash page size + 0000h. This

jump automatically drops PRIV to low.

Figure 2-8. Overview of Memory Regions

ULDR

UAPP

0000

TOP (128KB)

SYSTEMUSER

APPL

USER

LDR

RESET/STARTUP DEBUG LOCK

SYS PASSWORD

USR LDR START

IVT IVT IVT

STARTUP

USR LDR PASSWORD

USR APP START

10h

20h

+10h

STARTUP

USR APP PASSWORD

+10h

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 254 255

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