CY7C65013
CY7C65113
Document #: 38-08002 Rev. *B
Page 30 of 51
15.0
USB Overview
The USB hardware includes a USB Hub repeater with one upstream and up to seven downstream ports. The USB Hub repeater
interfaces to the microcontroller through a full-speed serial interface engine (SIE). An external series resistor of Rext must be
placed in series with all upstream and downstream USB outputs in order to meet the USB driver requirements of the USB
specification. The CY7C65x13 microcontroller can provide the functionality of a compound device consisting of a USB hub and
permanently attached functions.
15.1
USB Serial Interface Engine (SIE)
The SIE allows the CY7C65x13 microcontroller to communicate with the USB host through the USB repeater portion of the hub.
The SIE simplifies the interface between the microcontroller and USB by incorporating hardware that handles the following USB
bus activity independently of the microcontroller:
• Bit stuffing/unstuffing
• Checksum generation/checking
• ACK/NAK/STALL
• Token type identification
• Address checking.
Firmware is required to handle the following USB interface tasks:
• Coordinate enumeration by responding to SETUP packets
• Fill and empty the FIFOs
• Suspend/Resume coordination
• Verify and select DATA toggle values.
15.2
USB Enumeration
The internal hub and any compound device function are enumerated under firmware control. The hub is enumerated first, followed
by any integrated compound function. After the hub is enumerated, the USB host can read hub connection status to determine
which (if any) of the downstream ports need to be enumerated. The following is a brief summary of the typical enumeration
process of the CY7C65x13 by the USB host. For a detailed description of the enumeration process, refer to the USB specification.
In this description, ‘Firmware’ refers to embedded firmware in the CY7C65x13 controller.
1. The host computer sends a SETUP packet followed by a DATA packet to USB address 0 requesting the Device descriptor.
2. Firmware decodes the request and retrieves its Device descriptor from the program memory tables.
3. The host computer performs a control read sequence and Firmware responds by sending the Device descriptor over the USB
bus, via the on-chip FIFOs.
4. After receiving the descriptor, the host sends a SETUP packet followed by a DATA packet to address 0 assigning a new USB
address to the device.
5. Firmware stores the new address in its USB Device Address Register (for example, as Address B) after the no-data control
sequence completes.
6. The host sends a request for the Device descriptor using the new USB address.
7. Firmware decodes the request and retrieves the Device descriptor from program memory tables.
8. The host performs a control read sequence and Firmware responds by sending its Device descriptor over the USB bus.
9. The host generates control reads from the device to request the Configuration and Report descriptors.
10.Once the device receives a Set Configuration request, its functions may now be used.
11.Following enumeration as a hub, Firmware can optionally indicate to the host that a compound device exists (for example, the
keyboard in a keyboard/hub device).
12.The host carries out the enumeration process with this additional function as though it were attached downstream from the hub.
13.When the host assigns an address to this device, it is stored as the other USB address (for example, Address A).
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