
Preliminary W77LE58
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Example 4: Invalid Access
MOV
NOP
MOV
SETB EWT
TA, #0AAh
TA, #055h
3 M/C
1 M/C
3 M/C
2 M/C
In the first two examples, the writing to the protected bits is done before the 3 machine cycle window
closes. In Example 3, however, the writing to the protected bit occurs after the window has closed,
and so there is effectively no change in the status of the protected bit. In Example 4, the second write
to TA occurs 4 machine cycles after the first write, therefore the timed access window in not opened
at all, and the write to the protected bit fails.
ON-CHIP MTP ROM CHARACTERISTICS
The W77LE58 has several modes to program the on-chip MTP ROM. All these operations are
configured by the pins RST, ALE, PSEN, A9CTRL(P3.0), A13CTRL(P3.1), A14CTRL(P3.2),
OECTRL(P3.3), CE(P3.6), OE(P3.7), A0(P1.0) and V
PP
(EA ). Moreover, the A15
A0(P2.7
P2.0,
P1.7
P1.0) and the D7
D0(P0.7
P0.0) serve as the address and data bus respectively for these
operations.
Read Operation
This operation is supported for customer to read their code and the Security bits. The data will not be
valid if the Lock bit is programmed to low.
Output Disable Condition
When the OE is set to high, no data output appears on the D7..D0.
Program Operation
This operation is used to program the data to MTP ROM and the security bits. Program operation is
done when the V
PP
is reach to V
CP
(12.5V) level, CE set to low, and OE set to high.
Program Verify Operation
All the programming data must be checked after program operations. This operation should be
performed after each byte is programmed; it will ensure a substantial program margin.
Erase Operation
An erase operation is the only way to change data from 0 to 1. This operation will erase all the MTP
ROM cells and the security bits from 0 to 1. This erase operation is done when the V
PP
is reach to
V
EP
level, CE set to low, and OE set to high.
Erase Verify Operation
After an erase operation, all of the bytes in the chip must be verified to check whether they have been
successfully erased to 1 or not. The erase verify operation automatically ensures a substantial erase
margin. This operation will be done after the erase operation if V
PP
= V
EP
(14.5V), CE is high and
OE is low.