AN2556 Datasheet, PDF (26/35 Pages) STMicroelectronics – Porting an application from the ST10F269Zx to the ST10F273Z4

New registers
4
New registers
AN2556
4.1
4.1.1
XADRS3 register
On previous ST10 devices, this register was already present but its value was mask
programmed. On ST10F273Z4 this register has been made available to the user. In this way
the address range of the XRAM2 memory is now user programmable.
ST10F273Z4: XADRS3 (F01C_h)
SFR
Reset value: 800Bh
15 14 13 12 11 10 9 8 7
6
5
4
3
2
10
RGSAD
RGSZ
RW
RW
The register functionality is the same as the one of ADDRSELx registers used for external
address range selection with some limitations:
● The address window can only be located in the first Mbyte of addressable space, that
is, in the range 00’0000h-0F’FFFFh.
● The window start address must be aligned on a Range Size boundary.
Table 16.
Bit No.
3:0
15:4
XADRS3 register bits
Bit name
Function
Range size selection
RGSZ
Defines the size of the address window.
Range Start Address
RGSAD
Defines the bits A19..A8 of the Start Address of the address window.
Table 17. Definition of address area
Bit field Selected window Relevant bit (R) of
RGSZ
size
RGSAD
0000
256 bytes
RRRR RRRR RRRR
0001
512 bytes
RRRR RRRR RRRx
-
1010
-
256 Kbytes
-
RRxx xxxx xxxx
1011
512 Kbytes
Rxxx xxxx xxxx
11xx
Reserved
Selected range start address
relevant bit (R) of address (A23 - A0)
0000 RRRR RRRR RRRR xxxx xxxx
0000 RRRR RRRR RRRx xxxx xxxx
-
0000 RRxx xxxx xxxx xxxx xxxx
0000 Rxxx xxxx xxxx xxxx xxxx
Hardware impacts
None.
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