CY8C36_13 Datasheet, PDF (37/129 Pages) Cypress Semiconductor – Programmable System-on-Chip (PSoC®)

PSoC^® 3: CY8C36 Family Datasheet
The USBIO pins (P15[7] and P15[6]), when enabled for I/O mode, have limited drive mode control. The drive mode is set using the
PRT15.DM0[7, 6] register. A resistive pull option is also available at the USBIO pins, which can be enabled using the PRT15.DM1[7,
6] register. When enabled for USB mode, the drive mode control has no impact on the configuration of the USB pins. Unlike the GPIO
and SIO configurations, the port wide configuration registers do not configure the USB drive mode bits. Table 6-7 shows the drive
mode configuration for the USBIO pins.
Table 6-7. USBIO Drive Modes (P15[7] and P15[6])
PRT15.DM1[7,6]
Pull up enable
0
0
1
1
PRT15.DM0[7,6]
Drive Mode enable
0
1
0
1
PRT15.DR[7,6] = 1 PRT15.DR[7,6] = 0
Description
High Z
Strong High
Res High (5k)
Strong High
Strong Low
Strong Low
Strong Low
Strong Low
Open Drain, Strong Low
Strong Outputs
Resistive Pull Up, Strong Low
Strong Outputs
„ High Impedance Analog
The default reset state with both the output driver and digital
input buffer turned off. This prevents any current from flowing
in the I/O’s digital input buffer due to a floating voltage. This
state is recommended for pins that are floating or that support
an analog voltage. High impedance analog pins do not provide
digital input functionality.
To achieve the lowest chip current in sleep modes, all I/Os
must either be configured to the high impedance analog mode,
or have their pins driven to a power supply rail by the PSoC
device or by external circuitry.
„ High Impedance Digital
The input buffer is enabled for digital signal input. This is the
standard high impedance (HiZ) state recommended for digital
inputs.
„ Resistive pull-up or resistive pull-down
Resistive pull-up or pull-down, respectively, provides a series
resistance in one of the data states and strong drive in the
other. Pins can be used for digital input and output in these
modes. Interfacing to mechanical switches is a common
application for these modes. Resistive pull-up and pull-down
are not available with SIO in regulated output mode.
„ Open Drain, Drives High and Open Drain, Drives Low
Open drain modes provide high impedance in one of the data
states and strong drive in the other. Pins can be used for digital
input and output in these modes. A common application for
these modes is driving the I²C bus signal lines.
„ Strong Drive
Provides a strong CMOS output drive in either high or low
state. This is the standard output mode for pins. Strong Drive
mode pins must not be used as inputs under normal
circumstances. This mode is often used to drive digital output
signals or external FETs.
„ Resistive pull-up and pull-down
Similar to the resistive pull-up and resistive pull-down modes
except the pin is always in series with a resistor. The high data
state is pull-up while the low data state is pull-down. This mode
is most often used when other signals that may cause shorts
can drive the bus. Resistive pull-up and pull-down are not
available with SIO in regulated output mode.
6.4.2 Pin Registers
Registers to configure and interact with pins come in two forms
that may be used interchangeably.
All I/O registers are available in the standard port form, where
each bit of the register corresponds to one of the port pins. This
register form is efficient for quickly reconfiguring multiple port
pins at the same time.
I/O registers are also available in pin form, which combines the
eight most commonly used port register bits into a single register
for each pin. This enables very fast configuration changes to
individual pins with a single register write.
6.4.3 Bidirectional Mode
High speed bidirectional capability allows pins to provide both
the high impedance digital drive mode for input signals and a
second user selected drive mode such as strong drive (set using
PRT×DM[2:0] registers) for output signals on the same pin,
based on the state of an auxiliary control bus signal. The
bidirectional capability is useful for processor busses and
communications interfaces such as the SPI Slave MISO pin that
requires dynamic hardware control of the output buffer.
The auxiliary control bus routes up to 16 UDB or digital peripheral
generated output enable signals to one or more pins.
6.4.4 Slew Rate Limited Mode
GPIO and SIO pins have fast and slow output slew rate options
for strong and open drain drive modes, not resistive drive modes.
Because it results in reduced EMI, the slow edge rate option is
recommended for signals that are not speed critical, generally
less than 1 MHz. The fast slew rate is for signals between 1 MHz
and 33 MHz. The slew rate is individually configurable for each
pin, and is set by the PRT×SLW registers.
Document Number: 001-53413 Rev. *Q
Page 37 of 129