5
FN8193.2
October 12, 2006
Write in Process
The contents of the Data Registers are saved to
nonvolatile memory when the CS
pin goes from LOW
to HIGH after a complete write sequence is received
by the device. The progress of this internal write
operation can be monitored by a Write In Process bit
(WIP). The WIP bit is read with a Read Status
command.
INSTRUCTIONS
Identification (ID) Byte
The first byte sent to the X9410 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, for the
X9410 this is fixed as 0101[B] (refer to Figure 2).
The two least significant bits in the ID byte select one
of four devices on the bus. The physical device
address is defined by the state of the A
0
- A
1
input
pins. The X9410 compares the serial data stream with
the address input state; a successful compare of both
address bits is required for the X9410 to successfully
continue the command sequence. The A
0
- A
1
inputs
can be actively driven by CMOS input signals or tied to
V
CC
or V
SS
.
The remaining two bits in the ID byte must be set to 0.
Figure 2. Identification Byte Format
Instruction Byte
The next byte sent to the X9410 contains the
instruction and register pointer information. The four
most significant bits are the instruction. The next four
bits point to one of the two pots and when applicable
they point to one of four associated registers. The
format is shown below in Figure 3.
Figure 3. Instruction Byte Format
The four high order bits of the instruction byte specify
the operation. The next two bits (R
1
and R
0
) select one
of the four registers that is to be acted upon when a
register oriented instruction is issued. The last bit (P
0
)
selects which one of the two potentiometers is to be
affected by the instruction.
Four of the ten instructions are two bytes in length and
end with the transmission of the instruction byte.
These instructions are:
– XFR Data Register to Wiper Counter Register
—This
transfers the contents of one specified Data Register
to the associated Wiper Counter Register.
– XFR Wiper Counter Register to Data Register
—This
transfers the contents of the specified Wiper Coun-
ter Register to the specified associated Data Regis-
ter.
– Global XFR Data Register to Counter Register
—This
transfers the contents of both specified Data Registers
to the associated Wiper Counter Registers.
– Global XFR Wiper Counter Register to Data
Register—This transfers the contents of both Wiper
Counter Registers to the specified associated Data
Registers.
The basic sequence of the two byte instructions is
illustrated in Figure 4. These two-byte instructions
exchange data between the WCR and one of the data
registers. A transfer from a Data Register to a WCR is
essentially a write to a static RAM, with the static RAM
controlling the wiper position. The response of the
wiper to this action will be delayed by t
WRL
. A transfer
from the WCR (current wiper position), to a data
register is a write to nonvolatile memory and takes a
minimum of t
WR
to complete. The transfer can occur
between one of the two potentiometers and one of its
associated registers; or it may occur globally, where
the transfer occurs between both potentiometers and
one associated register.
100
0 0 A1 A0
Device Type
Identifier
Device Address
1
I1I2I3 I0 R1 R0 0 P0
Pot Select
Register
Select
Instructions
X9410
