X4643 XICOR [Xicor Inc.], X4643 Datasheet - Page 12

• Manufacturer Part Number: X4643
• Description: CPU Supervisor with 64K EEPROM
• Manufacturer: XICOR [Xicor Inc.]

X4643/5 – Preliminary Information
There is a similar operation, called “Set Current
Address” where the device does no operation, but
enters a new address into the address counter if a stop
is issued instead of the second start shown in Figure
13. The device goes into standby mode after the stop
and all bus activity will be ignored until a start is
detected. The next Current Address Read operation
reads from the newly loaded address. This operation
could be useful if the master knows the next address it
needs to read, but is not ready for the data.
Sequential 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 master now responds with an acknowledge, indi-
Figure 14. Sequential Read Sequence
X4643/5 Addressing
S
Following a start condition, the master must output a
Slave Address Byte. This byte consists of several parts:
– a device type identifier that is ‘1010’ to access the
– one bits of ‘0’.
– next two bits are the device address.
– one bit of the slave command byte is a R/W bit. The
REV 1.26 4/30/02
LAVE
array
R/W bit of the Slave Address Byte defines the opera-
tion to be performed. When the R/W bit is a one, then
a read operation is selected. A zero selects a write
operation. Refer to Figure 15.
Signals from
A
Signals from
DDRESS
the Slave
the Master
SDA Bus
B
YTE
Address
Slave
1
A
C
K
Data
(1)
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C
A
K
cating it requires additional data. The device continues
to output data for each acknowledge received. The
master terminates the read operation by not respond-
ing with an acknowledge and then issuing a stop con-
dition.
The data output is sequential, with the data from
address n followed by the data from address n + 1. The
address counter for read operations increments
through all page and column addresses, allowing the
entire memory contents to be serially read during one
operation. At the end of the address space the counter
“rolls over” to address 0000
to output data for each acknowledge received. Refer to
Figure 14 for the acknowledge and data transfer
sequence.
– After loading the entire Slave Address Byte from the
Word Address
The word address is either supplied by the master or
obtained from an internal counter. The internal counter
is undefined on a power up condition.
Data
(2)
SDA bus, the device compares the input slave byte
data to the proper slave byte. Upon a correct com-
pare, the device outputs an acknowledge on the SDA
line.
A
C
K
(n is any integer greater than 1)
Characteristics subject to change without notice.
Data
(n-1)
H
A
C
K
and the device continues
Data
(n)
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