AN2556 datasheet(27/35 Pages) STMICROELECTRONICS

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AN2556

New registers

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4.1.2

Software impacts

In the ST10F273Z4, this register should be programmed by the user before accessing

XRAM2 so that:

●

RGSZ defines a 128 Kbyte window size in order to cover the Flash registers and the

XRAM2 area: RGSZ = 1001b.

●

RGSAD defines bits 8 to 19 of the window start address that is the Flash registers area:

RGSAD = E00h.

The desired value should be written in XADRS3 register before enabling XRAM2 in

SYSCON and XPERCON registers.

Note:

XADRS3 cannot be changed after executing the EINIT instruction.

4.2

XPEREMU register

This register has been added as a write-only register.

The bit meaning is exactly the same as in the XPERCON register.

4.2.1

Hardware impacts

None.

4.2.2

Software impacts

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 X-Bus 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 such a

way the final configuration for X-Peripherals is stored in XPEREMU and used for the

emulation hardware setup.

ST10F273Z4: XPEREMU (EB7Eh)

XREG

Reset value: XXXXh

Reserved

XMIS

CEN

X12

CEN

XSS

CEN

XAS

CEN

XPW

MEN

Res

XRT

CEN

XRA

M2EN

XRA

M1EN

CAN

2EN

CAN

1EN

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