
The central processing unit (CPU)
UM0404
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DocID13284 Rev 2
When CAN1, CAN2, RTC, XASC, XSSC, I
2
C, XPWM and the XBUS Additional Features
are all disabled via XPERCON setting, then any access in the address range 00’E800h -
00’EFFFh will be directed to external memory interface, using the BUSCONx register
corresponding to address matching ADDRSELx register. All pins involved with X-
Peripherals, can be used as General Purpose IO whenever the related module is not
enabled.
The default X-Peripheral configuration after reset is such that only CAN1 and XRAM1 are
pre-selected: they will be enabled once XPEN bit in SYSCON register is set.
Register XPERCON cannot be changed after the global enabling of X-Peripherals, that is,
after setting of bit XPEN in SYSCON register.
In Emulation mode, all the X-Peripherals are enabled (XPERCON bits are all set). It is up to
the emulation device to redirect or not an access to external memory or to XBUS. Register
XPEREMU has been created to allow a dynamic selection of this redirection instead of a
static configuration of the emulator at the start-up.
Reserved bits of XPERCON register should always be written to ‘0’.
3.4.3
XPERCON and XPEREMU registers
As already mentioned, XPERCON register has to be programmed to enable the single
XBUS modules separately. The XPERCON is a read/write ESFR register; the XPEREMU
register is a write-only register mapped on XBUS memory space (address EB7Eh).
Once the XPEN bit of SYSCON register is set and at least one of the X-peripherals (except
memories) is activated, the register XPEREMU must be written with the same content of
XPERCON: this is mandatory in order to allow a correct emulation of the new set of features
XASCEN
XASC Enable Bit
‘0’: Accesses to the on-chip XASC are disabled, external access performed. Address
range 00’E900h-00’E9FFh is directed to external memory only if CAN1EN, CAN2EN,
XRTCEN, XASCEN, XI2CEN, XPWMEN and XMISCEN are ‘0’ also.
‘1’: The on-chip XASC is enabled and can be accessed.
XSSCEN
XSSC Enable Bit
‘0’: Accesses to the on-chip XSSC are disabled, external access performed. Address
range 00’E800h-00’E8FFh is directed to external memory only if CAN1EN, CAN2EN,
XRTCEN, XASCEN, XI2CEN, XPWMEN and XMISCEN are ‘0’ also.
‘1’: The on-chip XSSC is enabled and can be accessed.
XI2CEN
I
2
C Enable Bit
‘0’: Accesses to the on-chip I
2
C are disabled, external access performed. Address
range 00’EA00h-00’EAFFh is directed to external memory only if CAN1EN, CAN2EN,
XRTCEN, XASCEN, XSSCEN, XPWMEN and XMISCEN are ‘0’ also.
‘1’: The on-chip I2C is enabled and can be accessed.
XMISCEN
XBUS Additional Features Enable Bit
‘0’: Accesses to the Additional Miscellaneous Features is disabled. Address range
00’EB00h-00’EBFFh is directed to external memory only if CAN1EN, CAN2EN,
XRTCEN, XASCEN, XSSCEN, XPWMEN and XI2CEN are ‘0’ also.
‘1’: The Additional Features are enabled and can be accessed.
Bit
Function