cp3ub26 National Semiconductor Corporation, cp3ub26 Datasheet - Page 34

• Manufacturer Part Number: cp3ub26
• Description: Reprogrammable Connectivity Processor With Usb And Can Interfaces
• Manufacturer: National Semiconductor Corporation

www.national.com
8.4
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
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
8.4.2
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
WRPROT RDPROT ISPE
15
15
13
Function Word
Protection Word
INFORMATION BLOCK WORDS
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.
0
1
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.
12
–
–
Reserved
External USB transceiver forced into low-
power mode.
Transceiver power mode dependent on
USB controller status and programming
of the Function Word.
10
9
7
EMPTY
6
4
1
USB_ENABLE
3
BOOTAREA
0
1
0
34
EMPTY
ISPE
Table 14 lists all possible boot area encod-
ings.
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.
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
0.
BOOT
AREA
1111
1110
1101
1100
1011
1010
1001
1000
0111
0110
0101
0100
0011
0010
0001
0000
Table 14 Boot Area Encodings
No Boot Area defined
Size of the Boot
10K bytes
12K bytes
14K bytes
16K bytes
18K bytes
20K bytes
22K bytes
24K bytes
26K bytes
28K bytes
30K bytes
2K bytes
4K bytes
6K bytes
8K bytes
Area
Code Area
00 0000h
00 2800h
00 3000h
00 3800h
00 4000h
00 4800h
00 5000h
00 5800h
00 6000h
00 6800h
00 7000h
00 7800h
00 0800h
00 1000h
00 1800h
00 2000h
Address
Start