394
CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
Analog Interface
18.1.1
Analog Data Bus Interface
The Analog Data Bus Interface isolates the analog array and
analog system interface registers from the CPU system data
bus, to reduce bus loading. Transceivers are implemented
on the system data bus to isolate the analog data bus from
the system data bus. This creates a local analog data bus.
18.1.2
Analog Comparator Bus Interface
Each analog column has a dedicated comparator bus asso-
ciated with it. Every analog PSoC block has a comparator
output that can drive this bus. However, only one analog
block in a column can actively drive the comparator bus for a
column at any one time. The output on the comparator bus
drives into the digital blocks as a data input. It also serves as
an input to the decimator, as an interrupt input, and is avail-
able as read only data in the Analog Comparator Control
register (CMP_CR0).
illustrates one column of the comparator bus. In
the Continuous Time (CT) analog blocks, the CPhase and
CLatch bits of CT Block Control Register 2 determine
whether the output signal on the comparator bus is latched
inside the block, and if it is, which clock phase it is latched
on. In the Switched Capacitor (SC) analog blocks, the output
on the comparator bus is always latched. The ClockPhase
bit in SC Block Control Register 0 determines the phase on
which this data is latched and available.
The comparator bus is latched before it is available, to either
drive the digital blocks, interrupt, decimator, or for it to be
read in the CMP_CR0 register. The latch for each compara-
tor bus is transparent (the output tracks the input) during the
high period of PHI2. During the low period of PHI2, the latch
retains the value on the comparator bus during the high-to-
low transition of PHI2. The CMP_CR0 register is described
in the
“CMP_CR0 Register” on page 401
. There is also an
option to force the latch in each column into a transparent
mode by setting bits in the
register.
The CY8C28xxx PSoC devices have an additional compara-
tor synchronization option in which the 1X direct column
clock selection is used to synchronize the analog compara-
tor bus. This allows for higher frequency comparator sam-
pling.
As shown in
, the comparator bus output is gated
by the primary output of a selected digital block. This feature
is used to precisely control the integration period of an incre-
mental ADC. Any digital block can be used to drive the gate
signal. This selection may be made with the ICLKS bits in
registers DEC_CR0 and DEC_CR1. This function may be
enabled on a column-by-column basis, by setting the IGEN
bits in the
register.
The analog comparator bus output values can be modified
or combined with another analog comparator bus through
the Analog
function. The LUT takes
two inputs, A and B, and provides a selection of 16 possible
logic functions for those inputs. The LUT A and B inputs for
each column comparator output is shown in the following
table.
The LUT configuration is set in two control registers,
ALT_CR0 and ALT_CR1. Each selection for each column is
encoded in four bits. The function value corresponding to
the bit encoding is shown in the following table.
18.1.3
Analog Column Clock Generation
The analog array switched capacitor blocks require a two-
phase, non-overlapping clock. The switched cap blocks are
arranged in four columns, two to a column (a third block in
the column is a continuous time block).
An analog column clock generator is provided for each col-
umn and this clock is shared among the blocks in that col-
umn. The input clock source for each column clock
generator is selectable according to the
It is important to note that regardless of the clock source
selected, the output frequency of the column clock generator
is the input frequency divided by four. There are four selec-
tions for each column: V1, V2, ACLK0, and ACLK1. The V1
and V2 clock signals are global system clocks. Program-
ming options for these system clocks can be accessed in the
register. Each of the ACLK0 and ACLK1 clock
selections are driven by a selection of digital block outputs.
Table 18-1. A and B Inputs for Each Column Comparator
LUT Output
Comparator
LUT Output
A
B
4 Column PSoCs
Column 0
ACMP0
ACMP1
Column 1
ACMP1
ACMP2
Column 2
ACMP2
ACMP3
Column 3
ACMP3
ACMP0
2 Column PSoCs
Column 0
ACMP0
ACMP1
Column 1
ACMP1
0
Column 2
0
0
Column 3
0
ACMP0
Table 18-2. RDIxLTx Register
LUTx[3:0]
0h: 0000: FALSE
1h: 0001: A .AND. B
2h: 0010: A .AND. B
3h: 0011: A
4h: 0100: A .AND. B
5h: 0101: B
6h: 0110: A .XOR. B
7h: 0111: A .OR. B
8h: 1000: A .NOR. B
9h: 1001: A .XNOR. B
Ah: 1010: B
Bh: 1011: A .OR. B
Ch: 1100: A
Dh: 1101: A .OR. B
Eh: 1110: A. NAND. B
Fh: 1111: TRUE
Содержание CY8C28 series
Страница 65: ...64 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G RAM Paging ...
Страница 85: ...84 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Internal Main Oscillator IMO ...
Страница 93: ...92 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G External Crystal Oscillator ECO ...
Страница 97: ...96 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Phase Locked Loop PLL ...
Страница 125: ...124 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G ...
Страница 311: ...310 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G IDAC_CR0 1 FDh ...
Страница 317: ...316 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G ...
Страница 393: ...392 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G ...
Страница 425: ...424 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Analog Reference ...
Страница 461: ...460 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Two Column Limited Analog System ...
Страница 477: ...476 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Digital Clocks ...
Страница 483: ...482 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Multiply Accumulate MAC ...
Страница 513: ...512 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Internal Voltage Reference ...
Страница 523: ...522 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Switch Mode Pump SMP ...
Страница 533: ...532 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G I O Analog Multiplexer ...
Страница 537: ...536 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Real Time Clock RTC ...
Страница 561: ...560 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G ...