
X9271
Characteristics subject to change without notice.
7 of 23
REV 1.1.7 2/6/03
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DEVICE DESCRIPTION
Instructions
I
DENTIFICATION
B
YTE
(ID
AND
A)
The first byte sent to the X9271 from the host, following
a CS going HIGH to LOW, is called the Identification
byte. The most significant four bits of the slave address
are a device type identifier. The ID[3:0] bits is the
device id for the X9271; this is fixed as 0101[B] (refer to
Table 4).
The A1-A0 bits in the ID byte is the internal slave
address. The physical device address is defined by the
state of the A1-A0 input pins. The slave address is
externally specified by the user. The X9271 compares
the serial data stream with the address input state; a
successful compare of both address bits is required for
the X9271 to successfully continue the command
matches the incoming device address sent by the
master executes the instruction. The A1-A0 inputs can
be actively driven by CMOS input signals or tied to V
CC
or V
SS
.
I
NSTRUCTION
B
YTE
(I[3:0])
The next byte sent to the X9271 contains the
instruction and register pointer information. The three
most significant bits are used provide the instruction
opcode (I[3:0]). The RB and RA bits point to one of the
four Data Registers. P0 is the POT selection; since the
X9271 is single POT, the P0=0. The format is shown in
Table 5.
R
EGISTER
B
ANK
S
ELECTION
(R1, R0, P1, P0)
There are 16 registers organized into four banks. Bank
0 is the default bank of registers. Only Bank 0 registers
can be used for data register to Wiper Counter
Register operations.
Banks 1, 2, and 3 are additional banks of registers (12
total) that can be used for SPI write and read
operations. The data registers in Banks 1, 2, and 3
cannot be used for direct read/write operations
between the Wiper Counter Register.
Register Selection (DR0 to DR3) Table
Register Bank Selection (Bank 0 to Bank 3) Table
RB
0
RA
0
Register
Selection
0
Operations
Data Register Read and Write;
Wiper Counter Register
Operations
Data Register Read and Write;
Wiper Counter Register
Operations
Data Register Read and Write;
Wiper Counter Register
Operations
Data Register Read and Write;
Wiper Counter Register
Operations
0
1
1
1
0
2
1
1
3
P1
0
P0
0
Bank
Selection
0
Operations
Data Register Read and Write;
Wiper Counter Register
Operations
Data Register Read and Write
Only
Data Register Read and Write
Only
Data Register Read and Write
Only
0
1
1
1
0
2
1
1
3
Table 4. Identification Byte Format
ID3
0
(MSB)
ID2
1
ID1
0
ID0
1
0
0
A1
A0
(LSB)
Device Type
Identifier
Set to 0
for proper operation
Internal
Slave Address