AN2645 Freescale Semiconductor / Motorola, AN2645 Datasheet - Page 5

• Manufacturer Part Number: AN2645
• Description: Interfacing the Philips ISP1362 USB OTG Controller to the MCF5249
• Manufacturer: Freescale Semiconductor / Motorola

2.3
Standard series “A” (host) and series “B” (device) receptacles are present for host or device operation. Host
and device operation are fixed depending on the connector; no additional signals are required.
As USB OTG is intended for use in portable devices, the Mini-AB connector defines a dual-role device (acts
as host or device) and is physically smaller than the traditional series “A” and series “B” connectors. A
Mini-AB receptacle is attached to Port 1 for OTG operation.
The Mini-AB connector has an additional pin called the ID pin. The OTG default role of the ISP1362 is
controlled by the ID pin, which in turn is controlled by the type of plug connected into the Mini-AB
receptacle. If ID = LOW (mini-A plug connected), it becomes a host by default. If ID = HIGH (Mini-B plug
connected), it becomes a device by default.
The ID signal can be polled by the MCF5249 to check if it is being pulled high or low.
Please refer to the schematic summary note, Section 8, for more details on USB signals and connectors and
how they are used in this design.
2.4
The USB bus distributes 500 mA of power through each host port. Thus, low-power devices that might
normally require a separate AC adapter can be powered through the USB cable. However, a USB-OTG
enabled device must also be able to source power on Vbus as well, which is not practical for many
battery-powered devices, so the OTG supplement allows dual-role devices to supply as little as 8 mA to
meet the needs of the peripherals.
When operating in host mode, an over-current protection circuit is required on Vbus. This is implemented
on the daughter card with a Micrel dual-channel power distribution switch.
This is not required when operating in OTG or device mode, therefore Vbus is connected directly. OTG and
device mode also have to be Vbus sensing in order to detect when another USB device requests the start of
a session.
2.5
int[1:2] are connected to gpio[5:6] on the MCF5249. Pins GPIO5 and 6 on the MCF5249 have the primary
function of int[5:6].
2.6
The USB controller will be reset when the processor is reset with the RESET signal from the M5249C3
board. The reset time required for the ISP1362 is 10 ms. The reset signal from U9 (MAX6355LSUT-T) on
the M5249C3 is held active for 100 ms, which is well within the 10 ms requirement for the daughter card.
2.7
There are two wake-up pins, one dedicated to the device controller and one for the host controller
(D_SUSPD/WUP and H_SUSPD/WUP). This means that the controller can be placed in the suspend mode
when not in use and activated when required, thus saving power.
MOTOROLA
USB Connectors
USB Current Requirements
Interrupts
Reset
Suspend/Wake-up
Interfacing the Philips ISP1362 USB OTG to the MCF5249
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Hardware Design
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