Universal Serial Bus (USB)
Am186™CC/CH/CU Microcontrollers User’s Manual
18-3
.
18.3.1.1
USB Transceiver Interface
By default, the USB peripheral controller utilizes an integrated USB transceiver to directly
drive and receive data on the USBD+ and USBD– differential physical interface signals.
This transceiver allows a USB peripheral device to be designed with the Am186CC or
Am186CU microcontroller without requiring the additional board space needed by a discrete
transceiver device. The USB device terminator requirement is not integrated, so the
designer should add a single 1.5 K-
Ω
pullup resistor on the USBD+ signal to indicate this
is a full-speed device.
The USB specification requires a driver impedance between 29
Ω
and 44
Ω
on the USBD+
and USBD– signals. The CMOS drivers used have a much lower impedance, so matching
resistors must be placed in series on the USBD+ and USBD– signals as shown in
Figure 18-2 on page 18-4 and Figure 18-3 on page 18-5.
18.3.1.2
Programmable Connect and Disconnect
Because the microcontroller is meant to be in a self-powered application, there are a few
issues to resolve to meet USB specifications. For a full-speed device, the USB specification
requires a 1.5 K-
Ω
device terminator to a 3.0-V to 3.6-V voltage source on USBD+, derived
from or controlled by the power supplied by the USB cable (V
USB
), that does not supply
current when V
USB
is unpowered or removed. In a self-powered USB application, the USB
host/hub also cannot supply current to the USB device when the device is unpowered.
To help meet these criteria, the microcontroller is programmable to disable and three-state
the internal transceiver differential outputs. The other requirement is to disable the external
Table 18-1
USB Multiplexed Signals
Signal Function
Multiplexed
Signal(s)
Default
Signal
Internal USB Transceiver I/O Pins
USBD+
Internal USB transceiver differential input/output
UDPLS
USBD+
USBD–
Internal USB transceiver differential input/output
UDMNS
USBD–
External USB Transceiver I/O Pins
UDMNS
Status input from external transceiver
USBD–
USBD–
UDPLS
Status input from external transceiver
USBD+
USBD+
UTXDMNS
Output to the external transceiver differential
driver
RSVRD_102
RSVRD_102
UTXDPLS
Output to the external transceiver differential
driver
RSVRD_101
RSVRD_101
UXVOE
External transceiver transmit output enable
RSVRD_103
RSVRD_103
UXVRCV
Receive input from external transceiver
RSVRD_104
RSVRD_104
USB Clock Inputs
USBSCI
USB sample clock input
UCLK
USBSOF
PIO21
PIO21
USBSOF
USB start-of-frame synchronization output
UCLK
USBSCI
PIO21
PIO21
USBX1
USB peripheral controller crystal input
—
USBX1
USBX2
USB peripheral controller crystal output
—
USBX2
Содержание Am186 CC
Страница 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Страница 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...