at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 123

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Oscillator
Registers
106
AT89C51RE2
To optimize the power consumption and execution time needed for a specific task, an
internal prescaler feature has been implemented between the oscillator and the CPU
and peripherals.
Table 84. CKRL Register
CKRL – Clock Reload Register (97h)
Reset Value = 1111 1111b
Not bit addressable
Table 85. PCON Register
PCON – Power Control Register (87h)
SMOD1
CKRL7
Bit Number
Bit Number
7
7
7:0
7
6
5
4
3
2
1
0
SMOD0
CKRL6
6
6
Bit Mnemonic
Mnemonic
SMOD1
SMOD0
CKRL
POF
GF1
GF0
IDL
PD
-
CKRL5
5
-
5
Description
Clock Reload Register
Prescaler value
Description
Serial Port Mode bit 1
Set to select double baud rate in mode 1, 2 or 3.
Serial Port Mode bit 0
Cleared to select SM0 bit in SCON register.
Set to select FE bit in SCON register.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Power-off Flag
Cleared by software to recognize the next reset type.
Set by hardware when V
also be set by software.
General-purpose Flag
Cleared by software for general-purpose usage.
Set by software for general-purpose usage.
General-purpose Flag
Cleared by software for general-purpose usage.
Set by software for general-purpose usage.
Power-down Mode bit
Cleared by hardware when reset occurs.
Set to enter power-down mode.
Idle Mode bit
Cleared by hardware when interrupt or reset occurs.
Set to enter idle mode.
CKRL4
POF
4
4
CKRL3
GF1
3
3
CC
rises from 0 to its nominal voltage. Can
CKRL2
GF0
2
2
CKRL1
PD
1
1
7663B–8051–03/07
CKRL0
IDL
0
0