492
CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
Decimator
27.2.9
DECx_CR Registers
Bits 7 and 6: Mode[1:0].
These bits signify the mode of
operation of the type 2 decimator block. A ‘00’ in Mode
enables the user to configure the type 2 block to match a
type 1 behavior, where the input data stream is integrated
and an external firmware performs the resampling/differenti-
ation process required to complete the Sinc2 filtering. If
Mode is ‘01’, the decimator block can be used in an incre-
mental mode. For the type 1 decimator block, this function is
performed by bit 7 of DEC_CR1 register. If a decimator-
based incremental ADC is to be configured, the Mode bits
are set to ‘01’. The full algorithm (when Mode is set to ‘10’)
implies the usage of the decimator as a Sinc2 block, to be
used in delta-sigma ADCs. The selection of ‘11’ for Mode is
Reserved.
Bits 5 and 4: Data Out Shift[1:0].
The Data Output Shift
, which enumerates
the available operating modes. To compute the effective res-
olution, the following equations are used:
Single Modulator: (log2 (Decimation Rate) – 1) × 1.5
Double Modulator: (log2 (Decimation Rate) – 1) × 2
Bit 3: Data Format.
The Data Format bit can be weighted
as signed (2s complement output) or unsigned (offset binary
data).
Bits 2 to 0: Decimation Rate.
The devices with type 2 dec-
imator blocks have the choice of using an internal or exter-
nal timer. If an internal timer is used, the user can program
the Decimation Rate for the appropriate decimation rate or
simply use the external timer after setting the Decimation
Rate bits to zero.
For additional information, refer to the
.
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,D4h
Mode[1:0]
Data Out Shift[1:0]
Data Format
Decimation Rate[2:0]
RW : 00
1,D5h
Mode[1:0]
Data Out Shift[1:0]
Data Format
Decimation Rate[2:0]
RW : 00
1,D6h
Mode[1:0]
Data Out Shift[1:0]
Data Format
Decimation Rate[2:0]
RW : 00
1,D7h
Mode[1:0]
Data Out Shift[1:0]
Data Format
Decimation Rate[2:0]
RW : 00
Table 27-7. Decimator Data Output Shift
Decimation
Rate
Modulator
Type
Effective
Resolution
Shift
32
Single
6
4
32
Double
8
2
64
Single
*8 (7.5)
4
64
Double
10
2
128
Single
9
5
128
Double
12
2
256
Single
*11 (10.5)
5
256
Double
14
2
Содержание CY8C28 series
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