24AA65 Datasheet, PDF (8/12 Pages) Microchip Technology – 64K 1.8V I 2 C O Smart Serial O EEPROM

24AA65
byte would be 10XX0011. After the third byte is sent to
the device, it will acknowledge and a STOP bit is then
sent by the master to complete the command.
During a normal write sequence, if an attempt is made
to write to a protected address, no data will be written
and the device will not report an error or abort the com-
mand. If a write command is attempted across a
secure boundary, unprotected addresses will be written
and protected addresses will not.
5.8 Security Configuration Read
The status of the secure portion of memory can be read
by using the same technique as programming this
option except the READ bit (bit 6) of the configuration
byte is set to a one. After the configuration byte is sent,
the device will acknowledge and then send two bytes of
data to the master just as in a normal read sequence.
The master must acknowledge the first byte and not
acknowledge the second, and then send a stop bit to
end the sequence. The upper four bits of both of these
bytes will always be read as'1's. The lower four bits of
the first byte contains the starting secure block. The
lower four bits of the second byte contains the number
of secure blocks. The default starting secure block is fif-
teen and the default number of secure blocks is zero
(Figure 8-1).
6.0 ACKNOWLEDGE POLLING
Since the device will not acknowledge during a write
cycle, this can be used to determine when the cycle is
complete (this feature can be used to maximize bus
throughput). Once the stop condition for a write com-
mand has been issued from the master, the device ini-
tiates the internally timed write cycle. ACK polling can
be initiated immediately. This involves the master send-
ing a start condition followed by the control byte for a
write command (R/W = 0). If the device is still busy with
the write cycle, then no ACK will be returned. If the
cycle is complete, then the device will return the ACK
and the master can then proceed with the next read or
write command. See Figure 6-1 for flow diagram.
FIGURE 6-1: ACKNOWLEDGE POLLING
FLOW
Send
Write Command
Send Stop
Condition to
Initiate Write Cycle
Send Start
Send Control Byte
with R/W = 0
Did Device
Acknowledge
No
(ACK = 0)?
Yes
Next
Operation
DS21056F-page 8
© 1996 Microchip Technology Inc.