ML51/ML54/ML56
Sep. 01, 2020
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Rev 2.00
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TECHNI
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ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
6.1.7
Special Function Register (SFR)
The ML51/ML54/ML56 Series uses Special Function Registers (SFR) to control and monitor
peripherals and their modes. The SFR reside in the register locations 80 to FFH and are accessed by
direct addressing only. SFR those end their addresses as 0H or 8H are bit-addressable. It is very
useful in cases where user would like to modify a particular bit directly without changing other bits via
bit-field instructions. All other SFR are byte-addressable only. The ML51/ML54/ML56 Series contains
all the SFR presenting in the standard 8051. However some additional SFR are built in. Therefore,
some of unused bytes in the original 8051 have been given new functions. The SFR are listed below.
SFR Page Selection
6.1.7.1
To accommodate more than 128 SFR in the 0x80 to 0xFF address space, SFR paging has been
implemented. By default, all SFR accesses target SFR Page 0. During device initialization, some SFR
located on SFR Page 1 may need to be accessed. The register SFRS is used to switch SFR
addressing page.