CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
525
33. I/O Analog Multiplexer
This chapter explains the chip-wide I/O Analog Multiplexer for the CY8C28xxx PSoC
®
device and its associated registers. For
a complete table of the I/O Analog Multiplexer registers, refer to the
“Summary Table of the System Resource Registers” on
. For a quick reference of all PSoC registers in address order, refer to the
Register Details chapter on page 125
33.1
Architectural Description
The CY8C28x13, CY8C28x33, CY8C28x43, CY8C28x45,
and CY8C28x52 PSoC devices contain an enhanced analog
multiplexer (mux) capability. This function allows many I/O
pins to connect to a common internal analog bus. In these
devices, all I/O pins connect to this bus.
Any number of pins can be connected simultaneously, and
dedicated support circuitry allows selected pins to be alter-
nately charged high or connected to the bus. The analog
bus can be connected as an input into either the positive or
negative inputs of any analog continuous time (CT) block. A
block diagram is shown in
Figure 33-1. Analog Mux System
The Analog Mux Bus can be split into two separate nets, as
shown in
. The two analog mux nets can be con-
nected to different analog columns for simultaneous signal
processing.
33.1.1
IOMUX and GPIO
For each pin, the mux capability exists in parallel with the
normal GPIO cell described in the
and shown in
. Nor-
mally, the associated GPIO pin is put into a high-impedance
state for these applications, although there are cases where
the GPIO cell is configured by the user to briefly drive pin ini-
tialization states as described here.
Pins are individually connected to the internal bus by setting
the corresponding bits in the MUX_CRx registers. Any num-
ber of pins can be enabled at the same time. At reset, all of
these mux connections are open (disconnected).
Figure 33-2. I/O Pin Configuration
33.1.2
Dual Channel 8-Bit IDAC
The dual channel IDAC can provide two independent cur-
rent sources based on the input current reference IUNIT.
IUNIT is generated from PLL and can be trimmed in register
IDAC_CR1. These two current sources can vary from 0 to
637.5 µA with 255 steps (IDACL_D and IDACR_D), and
they are connected to analog mux bus left (AmuxBus0) and
analog mux bus right (AmuxBus1) independently. These two
current sources can act the same or independently due to
the value of ICEN in register IDAC_CR1.
Analog
Array
Digital
Blocks
Analog
Mux
Control
IO
Pin
PSoC Device
IO
Pin
IO
Pin
IO
Pin
An
alog
M
u
x Bu
s 1
An
alog
M
u
x Bu
s 0
GPIO
Pin
Switch Enable
(MUX_CRx.n)
Analog Mux Bus
Discharge
Clock
Vss
Break-
Before-Make
Circuitry
Содержание CY8C28 series
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