528
CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
I/O Analog Multiplexer
33.3.2
Chip-Wide Analog Input
The analog bus forms a multiplexer across many I/O pins.
This allows any of these pins to be brought into the analog
system for processing, as shown in
. The Port 0
pins are also brought through separate mux paths to the
continuous time block, so Port 0 inputs can be routed to the
analog system by either path.
In the CY8C28x13, CY8C28x33, CY8C28x43, CY8C28x45,
and CY8C28x52 PSoC devices, odd pins are connected to
AMUX Bus Left, and even pins to AMUX Bus Right. The two
mux buses can be shorted together using the switch con-
trolled by the SplitMux bit.
33.3.3
Crosspoint Switch
The bidirectional nature of the analog mux switches allows a
direct connection between any of the I/O pins, as shown in
. Enabling two (or more) pins at the same time
connects these pins together, with approximately 400 ohms
of resistance between each pin and the analog mux bus. As
long as the clock choice in the AMUX_CFGx registers is set
to the fixed '0' case, the switches will be static, controlled
only by the state of the individual switch enable bits in the
MUX_CRx registers. The crosspoint can be reconfigured at
any time and the user can provide a break-before-make
function with firmware if needed.
33.3.4
Charging Current
The analog mux bus can be connected to the dedicated
charging current. This enables applications such as capaci-
tor measurement with this current instead of charge sharing.
The IDAC_Dx and IDAC_CRx registers control this configu-
rable current. In the CY8C28x13, CY8C28x33, CY8C28x45,
and CY8C28x52 PSoC devices, there is a two-channel
IDAC.
33.4
Register Definitions
The following registers are only associated with the Analog Bus Mux in the CY8C28x13, CY8C28x33, CY8C28x43,
CY8C28x45, and CY8C28x52 PSoC devices and are listed in address order within their system resource configuration. For a
complete table of the I/O Analog Multiplexer registers, refer to the
“Summary Table of the System Resource Registers” on
. Each register description has an associated register table showing the bit structure for that register. Register bits
that are grayed out throughout this document are reserved bits and are not detailed in the register descriptions that follow.
Reserved bits should always be written with a value of ‘0’.
33.4.1
AMUX_CFG Register
The Analog Mux Configuration Register (AMUX_CFG) is
used to configure the clocked pre-charge mode of the ana-
log multiplexer system.
Bit 7: ABusMux1.
This bit selects the column 1 port input.
It picks between port 0 inputs or the analog mux bus right.
Bit 6: ABusMux0.
This bit selects the column 0 port input.
It picks between port 0 inputs or the analog mux bus left.
Bits 5 and 4: INTCAP[1:0].
These bits are used to choose
static connections to the analog mux bus even if the mux
clocking is enabled in the MUXCLKx[2:0] setting.
Bits 3 to 1: MUXCLK0[2:0].
These bits select the pre-
charge clock that drives the switching on the analog mux left
(AMuxBus0). The default choice is to have no clocking and
no precharge.
Bit 0: EN0.
This bit enables the clock output. When the
block is disabled, the output is ‘0’.
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
0,61h
ABusMux1
ABusMux0
INTCAP[1:0]
MUXCLK0[2:0]
EN0
RW : 0
Содержание CY8C28 series
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Страница 425: ...424 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Analog Reference ...
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