CAT5140_13 Datasheet, PDF (7/10 Pages) ON Semiconductor – Single Channel 256 Tap Digital Potentiometer (POT)

CAT5140
CAT5140 acknowledges once more and the Master
generates the STOP condition, at which time if a nonvolatile
data register is being selected, the device begins an internal
programming cycle to non-volatile memory. If the STOP
condition is not sent immediately after the last ACK the
internal non-volatile programming cycle doesn’t start.
While this internal cycle is in progress, the device will not
respond to any request from the Master device.
Write operations to volatile memory are completed during
the last bit of the data byte before the slave’s acknowledge.
The device will be ready for another command only after a
STOP condition sent by Master.
Acknowledge Polling
The disabling of the inputs can be used to take advantage
of the typical write cycle time. Once the stop condition is
issued to indicate the end of the host’s write operation, the
CAT5140 initiates the internal write cycle. ACK polling can
be initiated immediately. This involves issuing the start
condition followed by the slave address. If the CAT5140 is
still busy with the write operation, no ACK will be returned.
If the CAT5140 has completed the write operation, an
acknowledge will be returned and the host can then proceed
with the next instruction operation.
WRITE Protection
The Write Protection feature allows the user to protect
against inadvertent programming of the non-volatile data
registers. If the WP pin is tied to LOW, the data registers are
protected and become read only. Similarly, the WP pin going
low after start will interrupt a nonvolatile write to data
registers, while the WP pin going low after an internal write
cycle has started will have no effect on any write operation.
CAT5140 will accept slave addresses but the data registers
are protected from programming, which the device indicates
by failing to send an acknowledge after data is received.
READ Operation
A Read operation with a designated address consists of a
three byte instruction followed by one or more Data Bytes
(See Figure 3). The master initiates the operation issuing a
START, an Identification byte with the R/W bit set to “0”, an
Address Byte. Then the master sends a second START, and
a second Identification byte with the R/W bit set to “1”. After
each of the three bytes, the CAT5140 responds with an ACK.
Then CAT5140 transmits the Data Byte. The master then can
continue the read operation with the content of the next
register by sending acknowledge or can terminate the read
operation by issuing a NoACK followed by a STOP
condition after the last bit of a Data Byte.
Table 13. MEMORY MAP
Non-volatile
Address
Register
Default
Value
8
ACR
7
Reserved
6
General Purpose
00h
5
General Purpose
00h
4
General Purpose
00h
3
General Purpose
00h
2
General Purpose
00h
1
Device ID (read only)
D0h
0
IVR
80h
Volatile
Register
N/A
N/A
N/A
N/A
N/A
N/A
WR
If the master sends address 07h or addresses greater than
08h the slave responds with NoACK after the Memory
Address byte.
Address 8: Volatile Access Control Register − ACR (I/O)
The ACR bit 7 (VOL) toggles between Non-volatile and volatile registers accessed at address 00h. When VOL is Low (0),
the non-volatile IVR is accessed at address 00h. When VOL is high (1), the volatile Wiper Register is accessed at address 00h.
The initial default value for VOL = 0.
Bit
7
6
5
4
3
2
1
0
Name
0/1 VOL
0
0
0
0
0
0
0
00h and 80h are the only values that should be written to address 08h. For any other value written to address 08h the slave will
load only bit 7 but it will answer with a NoACK.
Address 7: RESERVED
The user should not read or write to this address. CAT5140 will respond with NoACK and it will take no action.
Address 07h can be accessed only in a sequential read and its content is FFh.
Address 6−2: Non-volatile General Purpose Memory (I/O)
8-bit Non-volatile Memory
Bit
Name
7
6
5
4
3
2
1
0
−
−
−
−
−
−
−
−
General Purpose Memories are preprogrammed at the factory to a default value of “00h”.
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