X9521 Datasheet, PDF (11/26 Pages) Xicor Inc. – Dual DCP, EEPROM Memory

X9521 – Preliminary Information
Signals from
the Master
SDA Bus
Signals from
the Slave
S
t
a
r
Slave
Address
t
WRITE Operation
S
Address
t
a
Byte
r
t
Slave
Address
READ Operation
S
t
o
p
10 1 0 0 0 0 0
A
C
K
1 0 1 0 0 0 01
A
A
C
C
K
K
Data
“Dummy” Write
Figure 15. Random EEPROM Address Read Sequence
the Device Type Identifier 1010111 or 1010010). Immedi-
ately after an operation to a DCP or CONSTAT Register is
performed, only a “Random EEPROM Read” is available.
Immediately following a “Random EEPROM Read” , a
“Current EEPROM Address Read” or “Sequential
EEPROM Read” is once again available (assuming that
no access to a DCP or CONSTAT Register occur in the
interim).
Random EEPROM Read
Random read operation allows the master to access any
memory location in the array. Prior to issuing the Slave
Address Byte with the R/W bit set to one, the master must
first perform a “dummy” write operation. The master
issues the START condition and the Slave Address Byte,
receives an ACKNOWLEDGE, then issues an Address
Byte. This “dummy” Write operation sets the address
pointer to the address from which to begin the random
EEPROM read operation.
After the X9521 acknowledges the receipt of the Address
Byte, the master immediately issues another START con-
dition and the Slave Address Byte with the R/W bit set to
one. This is followed by an ACKNOWLEDGE from the
X9521 and then by the eight bit word. The master termi-
nates the read operation by not responding with an
ACKNOWLEDGE and instead issuing a STOP condition
(Refer to Figure 15.).
A similar operation called “Set Current Address” also
exists. This operation is performed if a STOP is issued
instead of the second START shown in Figure 15. In this
case, the device sets the address pointer to that of the
Address Byte, and then goes into standby mode after the
STOP bit. All bus activity will be ignored until another
START is detected.
Sequential EEPROM Read
Sequential reads can be initiated as either a current
address read or random address read. The first Data Byte
is transmitted as with the other modes; however, the mas-
Signals from
the Master
SDA Bus
Signals from
the Slave
S
Slave
A
A
A
t
Address
C
C
C
o
K
K
K
p
0 0 01
A
C
Data
K
(1)
Data
(2)
Data
(n-1)
Data
(n)
(n is any integer greater than 1)
Figure 16. Sequential EEPROM Read Sequence
REV 1.1.9 1/30/03
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