MPC555
/
MPC556
CDR MoneT FLASH EEPROM
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
19-22
19.5.2 Program Margin Reads
The CMF EEPROM provides a program margin read with electrical margin for the pro-
gram state. Program margin reads provide sufficient margin to assure specified data
retention. The program margin read is enabled when SES = 1 and a programming
write has occurred. To increase the access time of the program margin read, the off-
page access time is four clocks instead of the usual two-clock off-page read access
time. The program margin read and subsequent on-page program verify reads return
a one for any bit that has not been completely programmed. Bits that the programming
write left in the non-programmed state return zero when read. Bits that have completed
programming return zero when read and update the data in the programming page
buffer so that no further programming of those bits will occur. The program margin
read occurs during the off-page read. A program margin read must be performed for
all pages that are being programmed after each program pulse.
S5
Program Margin Read Operation:
These reads determines if the state of the bits on
the selected page needs further modification by
the program operation. Once a bit is fully pro-
grammed, the data stored in the program page is
updated. No further programming occurs for that
bit, and the value read is a 0.
While it is not necessary to read all words on a
page to determine if another program pulse needs
to be applied, all pages being programmed must
be read once after each program pulse.
S4
T8
Write EHV = 1
S1
T9
Write SES = 0 or a master reset.
Table 19-10 Results of Programming Margin Read
Current Data in the Pro-
gram Page Buffer
1
NOTES:
1. 0 = bit needs further programming
1 = bit does not need further programming
Current State of Bit
Data Read During
Margin Read
2
2. A “0” read during the margin read means that the bit does NOT need further programming. A “1” means
the bit needs to be programmed further.
New Data for the
Program Page Buffer
1
0
Programmed (0)
0
1
0
Erased (1)
1
0
1
Programmed (0)
0
1
1
Erased (1)
0
1
Table 19-9 Program Interlock State Descriptions (Continued)
State
Mode
Next
State
Transition Requirement
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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