AS3525-A/-B C22O22
Data Sheet, Confidential
7.1.6 Boot Concept
It can be selected if the system should boot either using the internal ROM (internal boot loader) or an external ROM/Flash (connected to the MPMC
interface). XPC[0] is read within global chip reset to do the selection of either internal or external boot.
Table 11 Boot definitions for internal/external boot selection
XPC[0]
1
0
Booting Option
Internal ROM
External ROM/Flash
7.1.6.1 Internal Bootloader Version C22
Within the internal ROM boot loader several options for booting can be selected:
•
•
•
•
•
•
SSP IF - SPI master for ST serial flash types
SSP IF - SPI slave
NandFlash
Debug UART diagnostics
IDE boot: direct boot from harddisk
USB boot promer. In the case that a USB connection is present and either an update button is pressed or there is no
bootable device, the USB promer is started (see Figure 7 Boot decision between normal boot and USB boot promer” for
details). The USB boot promer allows update of the firmware by using an USB mass storage class device. This update can
be used either for initial programming (factory programming) or as mechanism for an in-field firmware update.
All boot loader options of the internal bootloader are configured by XPC[3:1] pins. External pull-up or pull-down resistors should be used to
configure the boot options.
Table 12 Boot definitions Chip version C22
XPC[3:1]
Boot Device
0
1
2
3
4
5
6
7
000
SPI master ST M25Pxx serial Nor Flash
SPI master Atmel AT45DB011B serial Nor Flash
SPI slave
NandFlash
IDE
reserved for developers mode
UART / Command Line Interface without diagnostics
UART / Command Line Interface with diagnostics
001
010
011
100
101
110
111
The update button is located between xpa[4] and xpa[0]. Within the key scan routine, xpa[4] is driven shortly to each logic level “0” and “1” and the
value of xpa[0] is read back to sense a keypress of the update button.
For the USB promer, it is necessary that frequency settings defining the quarz crystal frequency are defined by the pins xpa[6:4]. For details refer to
“Table 13 USB promer frequency settings”. These settings are read at the beginning in the initialisation routine of the bootloader.
Table 13 USB promer frequency settings
XPA[6:4]
USB promer frequency settings
000
24 MHz
001
20 MHz
010
13 MHz
011
12 MHz
100
10 MHz
others
reserved / defaults to 24 MHz
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