X9521 Datasheet, PDF (4/25 Pages) Xicor Inc. – Dual DCP, EEPROM Memory

X9521
SCL
from
1
Master
Data Output
from
Transmitter
8
9
Data Output
from
Receiver
Start
Acknowledge
Figure 3. Acknowledge Response From Receiver
minate further data transmissions if an ACKNOWLEDGE
is not detected. The master must then issue a STOP
condition to place the device into a known state.
DEVICE INTERNAL ADDRESSING
Addressing Protocol Overview
The user addressable internal components of the X9521
can be split up into three main parts:
—Two Digitally Controlled Potentiometers (DCPs)
—EEPROM array
—Control and Status (CONSTAT) Register
Depending upon the operation to be performed on each
of these individual parts, a 1, 2 or 3 Byte protocol is used.
All operations however must begin with the Slave
Address Byte being issued on the SDA pin. The Slave
address selects the part of the X9521 to be addressed,
and specifies if a Read or Write operation is to be per-
formed.
It should be noted that in order to perform a write opera-
tion to either a DCP or the EEPROM array, the Write
Enable Latch (WEL) bit must first be set (See “BL1, BL0:
Block Lock protection bits - (Nonvolatile)” on page 12.)
Slave Address Byte
Following a START condition, the master must output a
Slave Address Byte (Refer to Figure 4.). This byte con-
sists of three parts:
—The Device Type Identifier which consists of the most
significant four bits of the Slave Address (SA7 - SA4).
The Device Type Identifier must always be set to 1010
in order to select the X9521.
—The next three bits (SA3 - SA1) are the Internal Device
Address bits. Setting these bits to 000 internally
selects the EEPROM array, while setting these bits to
111 selects the DCP structures in the X9521. The
CONSTAT Register may be selected using the Inter-
nal Device Address 010.
—The Least Significant Bit of the Slave Address (SA0)
Byte is the R/W bit. This bit defines the operation to be
performed on the device being addressed (as defined
in the bits SA3 - SA1). When the R/W bit is “1”, then a
READ operation is selected. A “0” selects a WRITE
operation (Refer to Figure 4.)
SA7 SA6 SA5 SA4 SA3 SA2 _{SA1 SA0}
101 0
R/W
DEVICE TYPE
IDENTIFIER
INTERNAL
DEVICE
ADDRESS
READ /
WRITE
Internal Address
(SA3 - SA1)
000
010
111
Internally Addressed
Device
EEPROM Array
CONSTAT Register
DCP
Bit SA0
0
1
Operation
WRITE
READ
Figure 4. Slave Address Format
4
FN8207.1
August 25, 2005