Bit
Bit Number Mnemonic Description
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
CPU and peripheral clock bit
0
X2
Clear to select 12 clock periods per machine cycle (STD mode, FOSC=FXTAL/2).
Set to select 6 clock periods per machine cycle (X2 mode, FOSC=FXTAL).
Reset Value = XXXX XXX0b
Not bit addressable
For further details on the X2 feature, please refer to ANM072 available on the web
(http://www.atmel.com)
14 AT/TS8xC51Rx2
4188E–8051–08/06