28F001BX-T/28F001BX-B
BOOT BLOCK PROGRAM AND
ERASE
The boot block is intended to contain secure code
which will minimally bring up a system and control
programming and erase of other blocks of the de-
vice, if needed. Therefore, additional ‘‘lockout’’ pro-
tection is provided to guarantee data integrity. Boot
block program and erase operations are enabled
through high voltage V
HH
on either RP
Y
or OE
Y
,
and the normal program and erase command se-
quences are used. Reference the AC Waveforms for
Program/Erase.
If boot block program or erase is attempted while
RP
Y
is at V
IH
, either the Program Status or Erase
Status bit will be set to ‘‘1’’, reflective of the opera-
tion being attempted and indicating boot block lock.
Program/erase attempts while V
IH
k
RP
Y
k
V
HH
produce spurious results and should not be attempt-
ed.
In-System Operation
For on-board programming, the RP
Y
pin is the most
convenient means of altering the boot block. Before
issuing Program or Erase confirms commands, RP
Y
must transition to V
HH
. Hold RP
Y
at this high volt-
age throughout the program or erase interval (until
after Status Register confirm of successful comple-
tion). At this time, it can return to V
IH
or V
IL
.
290406–7
Bus
Command
Comments
Operation
Write
Program
Setup
Data
e
40H
Address
e
Byte to be
Programmed
Write
Program
Data to be programmed
Address
e
Byte to be
Programmed
Read
Status Register Data.
Toggle OE
Y
or CE
Y
to
update Status Register
Check SR.7
1
e
Ready, 0
e
Busy
Standby
Repeat for subsequent bytes.
Full status check can be done after each byte or after a
sequence of bytes.
Write FFH after the last byte programming operation to
reset the device to Read Array Mode.
Bus
Command
Comments
Operation
Standby
Check SR.3
1
e
V
PP
Low Detect
Standby
Check SR.4
1
e
Byte Program Error
SR.3 MUST be cleared, if set during a program attempt,
before further attempts are allowed by the Write State
Machine.
SR.4 is only cleared by the Clear Status Register
Command, in cases where multiple bytes are
programmed before full status is checked.
If error is detected, clear the Status Register before
attempting retry or other error recovery.
Figure 9. 28F001BX Byte Programming Flowchart
12