MCP2200
1.5
USB Transceiver
1.6
1.6.1
GPIO Module
CONFIGURABLE PIN FUNCTIONS
The MCP2200 has a built-in, USB 2.0, full-speed
transceiver internally connected to the USB module.
The USB transceiver obtains power from the V
USB
pin,
which is internally connected to the 3.3V regulator. The
best electrical signal quality is obtained when V
USB
is
locally bypassed with a high quality ceramic capacitor.
The GPIO Module is a standard 8-bit I/O port.
The pins can be configured as:
• GPIO – Individually configurable general purpose
input or output
• SSPND – USB Suspend state
• USBCFG – Indicates USB configuration status
• RxLED – Indicates USB receive traffic
• TxLED – Indicates USB transmit traffic
1.5.1
INTERNAL PULL-UP RESISTORS
The MCP2200 devices have built-in pull-up resistors
designed to meet the requirements for full-speed USB.
1.5.1.1
Bus Power Only
In Bus Power Only mode, all power for the application
is drawn from the USB (Figure
This is effectively
the simplest power method for the device.
In order to meet the inrush current requirements of the
USB 2.0 specifications, the total effective capacitance
appearing across VBUS and ground must be no more
than 10 µF. If not, some kind of inrush limiting is
required. For more details, see Section 7.2.4 of the
“Universal Serial Bus Specification”.
According to the USB 2.0 specification, all USB devices
must also support a Low-Power Suspend mode. In the
USB Suspend mode, devices must consume no more
than 500 µA (or 2.5 mA for high powered devices that
are remote wake-up capable) from the 5V V
BUS
line of
the USB cable.
The host signals the USB device to enter Suspend
mode by stopping all USB traffic to that device for more
than 3 ms.
During USB Suspend mode, the D+ or D- pull-up
resistor must remain active, which will consume some
of the allowed suspend current budget (500 µA/
2.5 mA).
1.6.1.1
SSPND Pin Function
The SSPND pin (if enabled) reflects the USB state
(Suspend/Resume). The pin is active ‘low’ when the
Suspend state has been issued by the USB host.
Likewise, the pin drives ‘high’ after the Resume state is
achieved.
This pin allows the application to go into Low Power
mode when USB communication is suspended, and
switches to a full active state when USB activity is
resumed.
1.6.1.2
USBCFG Pin Function
The USBCFG pin (if enabled) starts out ‘low’ during
power-up or after Reset, and goes ‘high’ after the
device successfully configures to the USB. The pin will
go ‘low’ when in Suspend mode and ‘high’ when the
USB resumes.
1.6.1.3
RxLED Pin Function (IN Message)
The ‘Rx’ in the pin name is in respect to the USB host.
The RxLED pin is an indicator for USB ‘IN’ messages.
This pin will either pulse low for a period of time
(configurable for ~100 ms or ~200 ms), or toggle to the
opposite state for every message received
(IN message) by the USB host. This allows the
application to count messages or provide a visual
indication of USB traffic.
FIGURE 1-2:
V
BUS
BUS POWER ONLY
V
DD
V
USB
V
SS
1.6.1.4
TxLED Pin Function (OUT Message)
The ‘Tx’ in the pin name is in respect to the USB host.
The TxLED pin is an indicator for USB ‘OUT’
messages.
This pin will either pulse low for a period of time
(configurable for ~100 ms or ~200 ms), or toggle to the
opposite state for every message transmitted (OUT
message) by the USB host. This allows the application
to count messages or provide a visual indication of
USB traffic.
DS22228A-page 6
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
