MPC555
/
MPC556
CDR MoneT FLASH EEPROM
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
19-34
the value of the NVM fuse. Reading CENSOR[0:1] while setting or clearing with the
high voltage applied (CSC = 1 and EHV = 1) will return zeroes.
The set operation changes the state in an NVM fuse from a zero to a one by program-
ming NVM bit 0 and erasing NVM bit 1 simultaneously in the NVM fuse. This set oper-
ation can be performed without changing the contents of the CMF array.
To set one or both of the bits in CENSOR[0:1],
1. Using section
19.7.6 A Technique to Determine SCLKR, CLKPE, and
, write the pulse width timing control fields for an erase pulse, CSC = 1,
PE = 0 and SES = 1 in the CMFCTL register.
2. Write a one to the CENSOR bit(s) to be set.
3. Write EHV = 1 in the CMFCTL register. This will apply the programming voltag-
es to NVM bit 0 and the erase voltages to NVM bit 1 simultaneously.
4. Read the CMFCTL register until HVS = 0.
5. Write EHV = 0 in the CMFCTL register.
6. Read the CMFMCR CENSOR bit(s) that are being set. If any bit selected for set
is a 0 go to step 3.
7. Write SES = 0 and CSC = 0.
The clear operation changes the state in an NVM fuse from a one to a zero by erasing
NVM bit 0 and programming NVM bit 1 simultaneously in the NVM fuse. This clear op-
eration can be done only while erasing the entire CMF array and shadow information.
To clear CENSOR[0:1],
1. Write PROTECT[0:7] = 0x00 to enable the entire array for erasure.
2. Using section
19.7.6 A Technique to Determine SCLKR, CLKPE, and
, write the pulse width timing control fields for an erase pulse,
BLOCK[0:7] = 0xFF, CSC = 1, PE = 1 and SES = 1 in the CMFCTL register.
3. Perform an erase interlock write.
4. Write EHV = 1 in the CMFCTL register. This will apply the erase voltages to the
entire CMF array and NVM bit 0 and the programming voltages to NVM bit 1
simultaneously.
5. Read the CMFCTL register until HVS = 0.
6. Write EHV = 0 in the CMFCTL register.
7. Read the entire CMF array and the shadow information words. If any bit equals
zero, go to step 4.
8. Read CENSOR[0:1]. If CENSOR[0:1]
≠
0 go to step 4.
9. Write SES = 0 and CSC = 0.
Table 19-17 NVM Fuse States
NVM bit 0
NVM bit 1
NVM Fuse Bit Value
Erased
Erased
Undefined
Programmed
Erased
Set (1)
Erased
Programmed
Cleared (0)
Programmed
Programmed
Undefined
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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