Preliminary
CAT24WC128
DEVICE ADDRESSING
knowledge, the CAT24WC128 will continue to transmit
data. IfnoacknowledgeissentbytheMaster, thedevice
terminates data transmission and waits for a STOP
condition.
The bus Master begins a transmission by sending a
START condition. The Master sends the address of the
particular slave device it is requesting. The seven most
significant bits of the 8-bit slave address are fixed as
1010XXX (Fig. 5), where X can be a 0 or 1. The last bit
of the slave address specifies whether a Read or Write
operation is to be performed. When this bit is set to 1, a
Read operation is selected, and when set to 0, a Write
operation is selected.
WRITE OPERATIONS
Byte Write
In the Byte Write mode, the Master device sends the
START condition and the slave address information
(with the R/W bit set to zero) to the Slave device. After
the Slave generates an acknowledge, the Master sends
two 8-bit address words that are to be written into the
address pointers of the CAT24WC128. After receiving
another acknowledge from the Slave, the Master device
transmits the data to be written into the addressed
memory location. The CAT24WC128 acknowledges
once more and the Master generates the STOP condi-
tion. At this time, the device begins an internal program-
ming cycle to nonvolatile memory. While the cycle is in
progress, thedevicewillnotrespondtoanyrequestfrom
the Master device.
After the Master sends a START condition and the slave
address byte, the CAT24WC128 monitors the bus and
responds with an acknowledge (on the SDA line) when
its address matches the transmitted slave address. The
CAT24WC128 then performs a Read or Write operation
depending on the state of the R/W bit.
Acknowledge
Afterasuccessfuldatatransfer, eachreceivingdeviceis
requiredtogenerateanacknowledge.TheAcknowledg-
ing device pulls down the SDA line during the ninth clock
cycle, signaling that it received the 8 bits of data.
Page Write
TheCAT24WC128respondswithanacknowledgeafter
receivingaSTARTconditionanditsslaveaddress. Ifthe
device has been selected along with a write operation,
it responds with an acknowledge after receiving each 8-
bit byte.
The CAT24WC128 writes up to 64 bytes of data, in a
single write cycle, using the Page Write operation. The
page write operation is initiated in the same manner as
the byte write operation, however instead of terminating
after the initial byte is transmitted, the Master is allowed
to send up to 63 additional bytes. After each byte has
been transmitted, CAT24WC128 will respond with an
When the CAT24WC128 begins a READ mode it trans-
mits 8 bits of data, releases the SDA line, and monitors
the line for an acknowledge. Once it receives this ac-
Figure 4. Acknowledge Timing
SCL FROM
MASTER
1
8
9
DATA OUTPUT
FROM TRANSMITTER
DATA OUTPUT
FROM RECEIVER
START
ACKNOWLEDGE
5020 FHD F06
Figure 5. Slave Address Bits
1
0
1
0
A2
X
A1
X
A0 R/W
X
X is Don't Care, can be a '0' or a '1'.
5
5027 FHD F07
Doc. No. 25060-00 6/99 S-1
CATALYST [ CATALYST SEMICONDUCTOR ]
