MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 283

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

8.9.3.2 Keep Alive Power Registers Lock Mechanism
MPC555
USER’S MANUAL
The MPC555 / MPC556 asserts the TEXP signal, if enabled, when the RTC or TB time
value matches the value programmed in the associated alarm register or when the PIT
or DEC value reaches zero. The TEXP signal is negated when the TEXPS status bit
is written to one.
The KAPWR power supply feeds the main crystal oscillator (OSCM). The condition for
the main crystal oscillator stability is that the power supply value changes slowly. The
maximum slope must be less than 5 mV per oscillation cycle (
The USIU timer, clocks, reset, power, decrementer, and time base registers are pow-
ered by the KAPWR supply. When the main power supply is disconnected after power-
down mode is entered, the value stored in any of these registers is preserved. If pow-
er-down mode is not entered before power disconnect, there is a chance of data loss
in these registers. To minimize the possibility of data loss, the MPC555 / MPC556 in-
cludes a key mechanism that ensures data retention as long as a register is locked.
While a register is locked, writes to this register are ignored.
Each of the registers in the KAPWR region have a key that can be in one of two states:
open or locked. At power-on reset the following keys are locked: RTC, RTSEC, RT-
/
MPC556
MPC555
Figure 8-11 External Power Supply Scheme
TEXP
KAPWR
VDDSYN
VDD
VDDSRAM
CLOCKS AND POWER CONTROL
Switch
Logic
Rev. 15 October 2000
O
O
O
O
SW1
SW2
3 V - 3.3 V
Backup
Supply
Power
τ
Power Supply
Main Power
VDDSRAM
> 200-300/freq
Supply
3.3 V
3.3 V
MOTOROLA
oscm
8-23
).