X9261 Datasheet, PDF (7/21 Pages) Intersil Corporation – Single Supply/Low Power/256-Tap/SPI Bus

X9261
Table 1. Wiper Counter Register, WCR (8-bit), WCR[7:0]: Used to store the current wiper position (Volatile, V).
WCR7
WCR6
WCR5
WCR4
WCR3
WCR2
WCR1
WCR0
V
V
V
V
V
V
V
V
(MSB)
(LSB)
Table 2. Data Register, DR (8-bit), Bit [7:0]: Used to store wiper positions or data (Nonvolatile, NV).
Bit 7
NV
MSB
Bit 6
NV
Bit 5
NV
Bit 4
NV
Bit 3
NV
Bit 2
NV
Bit 1
NV
Bit 0
NV
LSB
DEVICE DESCRIPTION
Instructions
IDENTIFICATION BYTE ( ID AND A )
The first byte sent to the X9261 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 X9261; this is fixed as
0101[B] (refer to Table 3).
The AD[3:0] bits in the ID byte is the internal slave
address. The physical device address is defined by
the state of the A3 - A0 input pins. The slave address
is externally specified by the user. The X9261
compares the serial data stream with the address
Table 3. Identification Byte Format
Device Type
Identifier
input state; a successful compare of both address bits
is required for the X9261 to successfully continue the
command sequence. Only the device which slave
address matches the incoming device address sent
by the master executes the instruction. The A3-A0
inputs can be actively driven by CMOS input signals
or tied to V_CC or V_SS.
INSTRUCTION BYTE ( I[3:0] )
The next byte sent to the X9261 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 of each associated XDCP. The least
significant bit points to one of two Wiper Counter
Registers or Pots.The format is shown below in Table 4.
Slave Address
ID3
ID2
ID1
ID0
A3
A2
A1
A0
0
1
0
1
(MSB)
(LSB)
Table 4. Instruction Byte Format
Instruction
Opcode
I3
I2
I1
I0
(MSB)
Data
Register
Selection
RB
RA
Pot Selection
(WCR Selection)
0
P0
(LSB)
7
FN8171.2
September 14, 2005