CP3UB26 datasheet(34/268 Pages) NSC

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8.4

INFORMATION BLOCK WORDS

Two words in the information blocks are dedicated to hold

settings that affect the operation of the system: the Function

Word in Information Block 0 and the Protection Word in In-

formation Block 1.

8.4.1

Function Word

The Function Word resides in the Information Block 0 at ad-

dress 07Eh. At reset, the Function Word is copied into the

FMAR0 register.

USB_ENABLE The USB_ENABLE bit can be used to force

an external USB transceiver into its low-power

mode. The power mode is dependent on the

USB controller status, the USB_ENABLE bit

in the MCFG register (see Section 7.1), and

the USB_ENABLE bit in the Function Word.

– External USB transceiver forced into low-

power mode.

– Transceiver power mode dependent on

USB controller status and programming

of the Function Word.

8.4.2

Protection Word

The Protection Word resides in Information Block 1 at ad-

dress 0FEh. At reset, the Protection Word is copied into the

FMAR1 register.

BOOTAREA The BOOTAREA field specifies the size of the

Boot Area. The Boot Area starts at address 0

and ends at the address specified by this field.

The inverted bits of the BOOTAREA field

count the number of 2048-byte blocks to be

reserved as the Boot Area. The maximum

Boot Area size is 30K bytes (address range 0

to 77FFh). The end of the Boot Area defines

the start of the Code Area. If the device starts

in ISP mode and there is no Boot Area defined

(encoding 1111b), the device is kept in reset.

Table 14 lists all possible boot area encod-

ings.

EMPTY

The EMPTY field indicates whether the flash

program memory has been programmed or

should be treated as blank. If a majority of the

three EMPTY bits are clear, the flash program

memory is treated as programmed. If a major-

ity of the EMPTY bits are set, the flash pro-

gram memory is treated as empty. If the

ENV[1:0] inputs (see Section 6.1) are sam-

pled high at reset and the EMPTY bits indicate

the flash program memory is empty, the de-

vice will begin execution in ISP mode. The de-

vice enters ISP mode without regard to the

EMPTY status if ENV0 is driven low and

ENV1 is driven high.

ISPE

The ISPE field indicates whether the Boot

Area is used to hold In-System-Programming

routines or user application routines. If a ma-

jority of the three ISPE bits are set, the Boot

Area is intended to store ISP routines. If ma-

jority of the ISPE bits are clear, the Boot Area

holds user application routines. Table 15 sum-

marizes all possible EMPTY, ISPE, and Boot

Area settings and the corresponding start-up

operation for each combination. In DEV

mode, the EMPTY bit settings are ignored and

the CPU always starts executing from address

Reserved

USB_ENABLE

WRPROT RDPROT

ISPE

EMPTY

BOOTAREA

Table 14

Boot Area Encodings

BOOT

AREA

Size of the Boot

Area

Code Area

Start

Address

1111

No Boot Area defined

00 0000h

1110

2K bytes

00 0800h

1101

4K bytes

00 1000h

1100

6K bytes

00 1800h

1011

8K bytes

00 2000h

1010

10K bytes

00 2800h

1001

12K bytes

00 3000h

1000

14K bytes

00 3800h

0111

16K bytes

00 4000h

0110

18K bytes

00 4800h

0101

20K bytes

00 5000h

0100

22K bytes

00 5800h

0011

24K bytes

00 6000h

0010

26K bytes

00 6800h

0001

28K bytes

00 7000h

0000

30K bytes

00 7800h

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