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MPC555
/
MPC556
CDR MoneT FLASH EEPROM
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
19-27
during the erase margin read while the shadow information is read. For the erase op-
eration to be completed, block zero must also be fully verified.
NOTE
Setting the SIE bit disables normal array access. SIE should be
cleared after verifying the shadow information.
19.7 Voltage Control for Programming and Erasing
Bits for controlling the voltage during programming and erasing are found in the CM-
FCTL register.
19.7.1 Pulse Status
During a program or erase pulse, the HVS bit is set while the pulse is active or during
recovery. The BIU does not acknowledge an access to an array location if HVS = 1.
While HVS = 1, SES cannot be changed. The program or erase pulse becomes active
by setting the EHV bit and is terminated by clearing EHV or by the pulse width timing
control.
Figure 19-5 Pulse Status Timing
The recovery time is the time required for the CMF EEPROM to remove the program
or erase voltage from the array or shadow information before switching to another
mode of operation. The recovery time is determined by the system clock range
(SCLKR[0:2]) and the PE bit. If SCLKR = 000, the recovery time is 128 clocks. Other-
wise, the recovery time is 48 periods of the scaled clock.
Once reset is completed HVS will indicate no program or erase pulse (HVS = 0).
19.7.2 Pulse Width Timing Equation
To control the pulse widths for program and erase operations, the CMF EEPROM uses
the system clock and the timing control in CMFCTL. The total pulse time is defined by
the following pulse width equation:
EHV
HVS
Recovery
Pulse Width
Recovery = 48 Scaled Clocks or 128 Clocks
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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