
16
AT89C51ID2
4289C–8051–11/05
Table 19. PCON Register
PCON - Power Control Register (87h)
Reset Value = 00X1 0000b
Not bit addressable
76
543
210
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
Bit
Number
Bit
Mnemonic
Description
7SMOD1
Serial port Mode bit 1
Set to select double baud rate in mode 1, 2 or 3.
6SMOD0
Serial port Mode bit 0
Cleared to select SM0 bit in SCON register.
Set to select FE bit in SCON register.
5-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4POF
Power-Off Flag
Cleared to recognize next reset type.
Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set
by software.
3GF1
General purpose Flag
Cleared by software for general purpose usage.
Set by software for general purpose usage.
2GF0
General purpose Flag
Cleared by software for general purpose usage.
Set by software for general purpose usage.
1PD
Power-Down mode bit
Cleared by hardware when reset occurs.
Set to enter power-down mode.
0IDL
Idle mode bit
Cleared by hardware when interrupt or reset occurs.
Set to enter idle mode.