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CAT524 Folha de dados(PDF) 6 Page - Catalyst Semiconductor

Nome de Peças. CAT524
descrição  Configured Digitally Programmable Potentiometer
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Fbricantes  CATALYST [Catalyst Semiconductor]
Página de início  http://www.catalyst-semiconductor.com
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CAT524 Folha de dados(HTML) 6 Page - Catalyst Semiconductor

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CAT524
6
Doc. No. 2006, Rev. E
(CS) and Program (PROG). With CS high, a start bit
followed by a two bit DPP address and eight data bits are
clocked into the DPP control register via the DI pin. Data
enters on the clock’s rising edge.
The DPP output
changes to its new setting on the clock cycle following
D7, the last data bit.
Programming is achieved by bringing PROG high for a
minimum of 3 ms. PROG must be brought high sometime
after the start bit and at least 150 ns prior to the rising
edge of the clock cycle immediately following the D7 bit.
Two clock cycles after the D7 bit the DPP wiper control
register will be ready to receive the next set of address
and data bits. The clock must be kept running throughout
the programming cycle. Internal control circuitry takes
care of ramping the programming voltage for data transfer
to the non-volatile cells.
The CAT524 non-volatile
memory cells will endure over 100,000 write cycles and
will retain data for a minimum of 20 years without being
refreshed.
READING DATA
Each time data is transferred into a DPP wiper control
register currently held data is shifted out via the D0 pin,
thus in every data transaction a read cycle occurs. Note,
however, that the reading process is destructive. Data
must be removed from the register in order to be read.
Figure 2 depicts a Read Only cycle in which no change
occurs in the DPP’s output. This feature allows
µPs to
poll DPPs for their current setting without disturbing the
output voltage but it assumes that the setting being read
is also stored in non-volatile memory so that it can be
restored at the end of the read cycle. In Figure 2 CS
returns low before the 13th clock cycle completes. In
doing so the non-volatile memory setting is reloaded into
the DPP wiper control register.
VREF
VREF, the voltage applied between pins VREFH andVREFL,
sets the configured DPP’s Zero to Full Scale output
range where VREFL = Zero and VREFH = Full Scale. VREF
can span the full power supply range or just a fraction of
it. In typical applications VREFH andVREFL are connected
across the power supply rails. When using less than the
full supply voltage VREFH is restricted to voltages between
VDD and VDD/2 and VREFL to voltages between GND and
VDD/2.
READY
/BUSY
/BUSY
/BUSY
/BUSY
/BUSY
When saving data to non-volatile memory, the Ready/
Busy ouput (RDY/
BSY) signals the start and duration of
the non-volatile erase/write cycle. Upon receiving a
command to store data (PROG goes high) RDY/
BSY
goes low and remains low until the programming cycle
is complete. During this time the CAT524 will ignore any
data appearing at DI and no data will be output on DO.
RDY/
BSY is internally ANDed with a low voltage detector
circuit monitoring VDD. If VDD is below the minimum value
required for non-volatile programming, RDY/
BSY will
remain high following the program command indicating
a failure to record the desired data in non-volatile memory.
DATA OUTPUT
Data is output serially by the CAT524, LSB first, via the
Data Out (DO) pin following the reception of a start bit
and two address bits by the Data Input (DI).
DO
becomes active whenever CS goes high and resumes
its high impedance Tri-State mode when CS returns low.
Tri-Stating the DO pin allows several 524s to share a
single serial data line and simplifies interfacing multiple
524s to a microprocessor.
WRITING TO MEMORY
Programming the CAT524’s non-volatile memory is
accomplished through the control signals: Chip Select
Figure 2. Reading from Memory
Figure 1. Writing to Memory
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
D0
D1
D2
D3
D4
D5
D6
D7
1
NEW DPP DATA
CURRENT DPP DATA
CURRENT
NON-VOLATILE
DPP
OUTPUT
PROG
DO
DI
CS
NEW
VOLATILE
NEW
NON-VOLATILE
t
1
2
3
4
5
6
7
8
9
10
11
12
N
N+1 N+2
o
DPP VALUE
DPP VALUE
DPP VALUE
A0
A1
1
DO
DI
CS
PROG
DPP
OUTPUT
t
1
2
3
4
5
6
7
8
9
10
11
12
o
CURRENT
DPP VALUE
NON-VOLATILE
D0
D1
D2
D3
D4
D5
D6
D7
CURRENT DPP DATA


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