TS80C31X2 Datasheet, PDF (25/42 Pages) ATMEL Corporation – 8-bit CMOS Microcontroller ROMless

TS80C31X2
6.8 Power-Off Flag
The power-off flag allows the user to distinguish between a “cold start” reset and a “warm start” reset.
A cold start reset is the one induced by V_CC switch-on. A warm start reset occurs while V_CC is still applied to
the device and could be generated for example by an exit from power-down.
The power-off flag (POF) is located in PCON register (See Table 13.). POF is set by hardware when V_CC rises
from 0 to its nominal voltage. The POF can be set or cleared by software allowing the user to determine the type
of reset.
The POF value is only relevant with a Vcc range from 4.5V to 5.5V. For lower Vcc value, reading POF bit will
return indeterminate value.
Table 13. PCON Register
PCON - Power Control Register (87h)
7
6
5
4
3
2
1
0
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
Bit
Number
7
Bit
Mnemonic
Description
SMOD1
Serial port Mode bit 1
Set to select double baud rate in mode 1, 2 or 3.
Serial port Mode bit 0
6
SMOD0
Clear to select SM0 bit in SCON register.
Set to to select FE bit in SCON register.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Power-Off Flag
4
POF
Clear to recognize next reset type.
Set by hardware when V_CC rises from 0 to its nominal voltage. Can also be set by software.
General purpose Flag
3
GF1
Cleared by user for general purpose usage.
Set by user for general purpose usage.
General purpose Flag
2
GF0
Cleared by user for general purpose usage.
Set by user for general purpose usage.
Power-Down mode bit
1
PD
Cleared by hardware when reset occurs.
Set to enter power-down mode.
Idle mode bit
0
IDL
Clear by hardware when interrupt or reset occurs.
Set to enter idle mode.
Reset Value = 00X1 0000b
Not bit addressable
Rev. C - 15 January, 2001
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