Register set
ST10F276E
When CAN1, CAN2, RTC, XASC, XSSC, I2C, XPWM and the XBUS Additional Features are
all disabled via XPERCON setting, then any access in the address range 00’E800h -
00’EFFFh is directed to external memory interface, using the BUSCONx register
corresponding to the address matching ADDRSELx register. All pins used for X-Peripherals
can be used as General Purpose I/O whenever the related module is not enabled.
The default XPER selection after Reset is such that CAN1 is enabled, CAN2 is disabled,
XRAM1 (2 Kbyte XRAM) is enabled and XRAM2 (64 Kbyte XRAM) is disabled; all the other
X-Peripherals are disabled after Reset.
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). The
bondout chip determines whether or not to redirect an access to external memory or to
XBUS.
Reserved bits of XPERCON register are always written to ‘0’.
Table 85 below summarizes the Segment 8 mapping that depends upon the EA pin status
during reset as well as the SYSCON (bit XPEN) and XPERCON (bits XRAM2EN and
XFLASHEN) registers user programmed values.
.
Table 85. Segment 8 address range mapping
EA
XPEN
XRAM2EN
XFLASHEN
Segment 8
External memory
0
0
0
0
1
0
1
1
1
x
x
0
1
x
x
x
0
x
1
x
External memory
Reserved
Reserved
IFlash (B1F1)
Note:
The symbol “x” in the table above stands for “do not care”.
22.12
XPERCON and XPEREMU registers
As already mentioned, the XPERCON register must 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 introduced on XBUS for the new ST10 generation. The following instructions must
be added inside the initialization routine:
if (SYSCON.XPEN && (XPERCON & 0x07D3))
then { XPEREMU = XPERCON }
Of course, XPEREMU must be programmed after XPERCON and after SYSCON; in this
way the final configuration for X-Peripherals is stored in XPEREMU and used for the
emulation hardware setup.
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Doc ID 12303 Rev 3
STMICROELECTRONICS [ ST ]
