AN2556 datasheet(25/35 Pages) STMICROELECTRONICS

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AN2556

Modified registers

25/35

Access to the X-Peripherals are configured through three pairs of specific X-Bus

configuration registers, equivalent to the External Bus register BUSCONx and ADDRSELx.

Therefore several X-Peripherals sharing the same pair leading to the point that accesses a

disabled X-Peripheral are only redirected to external memory if all the other X-Peripherals

sharing the same pair of registers are disabled.

This gives the following groups:

●

CAN1, CAN2, XASC, XSSC, XI2C, XPWM, XRTC and XMISC: accessing to range

00’E800h-00’EFFFh are redirected to external memory only if all corresponding bits

are cleared.

●

XRAM1: accessing to range 00’E000h-00’E7FFh are redirected to external memory if

bit XRAM1EN is cleared.

●

XRAM2, XFLASH: accessing to range 09’0000h-0F’FFFFh (default value in XADRS3

memory if bits XRAM2EN and XFLASHEN are cleared.

3.1.1

Hardware impacts

None.

3.1.2

Software impacts

None, if ST10F269Zx software is not written to the reserved bit.

XFLASHEN

XFlash Enable Bit

0: Access to the Flash Registers are disabled. The on-chip Flash cannot be

programmed.

1: Access to the Flash Registers are enabled. The on-chip Flash can be

programmed.

XPWMEN

XPWM Enable

0: Access to the XPWM module is disabled, external access performed.

1: The XPWM module is enabled and can be accessed.

XASCEN

XASC Enable Bit

0: Access to the XASC is disabled, external access performed.

1: The XASC is enabled and can be accessed.

XSSCEN

XSSC Enable Bit

0: Access to the XSSC is disabled, external access performed.

1: The XSSC is enabled and can be accessed.

9X12CEN

X12C Enable Bit

0: Access to the X12C is disabled, external access performed.

1: The X12C is enabled and can be accessed.

XMISCEN

XBUS Additional Features Enable Bit

0: Access to the Additional Miscellaneous Features is disabled.

1: The Additional Features are enabled and can be accessed.

11:15

Reserved

Table 15.

XPERCON register description (continued)

Bit

Bit name

Function

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