Circuit for testing a USB device using a packet to be measured controlled by test signals
View Patent ↗A USB test circuit for use in a USB device such as a system LSI with a USB function for testing the USB function generates and outputs a packet to be measured for a signal quality test. In the test circuit, a test signal including a test_sin signal carrying operation mode information is inputted via a serial interface to a serial interface block, and a packet to be measured is generated by a data pattern generation block and a transmission data delivery block depending on the operation mode information. The packet to be measured is outputted via a UTMI interface to a USB PHY layer. Thus, a packet to be measured for a signal quality test is generated and outputted without receiving packets not to be measured such as a SETUP packet and a DATA packet, thereby reducing the test time.
1. A USB (Universal Serial Bus) test circuit incorporated in a USB device for actualizing a USB connection and used for a compliance test of the USB device, said circuit comprising:
an input portion that receives from an external device a test signal including operation mode information of said circuit and a timing signal synchronized with each bit data of the operation mode information; and
a generation portion that generates a packet to be measured for testing signal quality and outputs the packet,
said input portion receiving the operation mode information including a packet type of the packet to be measured which is desired to be generated, an endless flag that indicates whether or not to repeatedly generate and output the packet to be measured and a number of transmission bytes per packet of the packet to be measured which is desired to be generated, and extracting each bit data of the operation mode information at a timing corresponding to the timing signal and synchronized with a clock signal in the USB device,
said generation portion generating the packet to be measured depending on the operation mode information inputted to said input portion.
2. The USB test circuit in accordance with claim 1 , wherein said generation portion outputs the packet to be measured via a UTMI interface (USB2.0 Transceiver Macrocell Interface) to a physical layer of the USB device.
3. The USB test circuit in accordance with claim 1 , wherein the USB device operates in a mode selected from a plurality of transfer rate modes, and
said generation portion generates the packet to be measured depending on one of the transfer rate modes which is selected in the USB device.
4. The USB test circuit in accordance with claim 3 , wherein the transfer rate modes include full speed, low speed, and high speed modes.
5. The USB test circuit in accordance with claim 3 , wherein said generation portion determines a plurality of data patterns in advance, selects one of the data patterns depending on the operation mode information, and generates the packet to be measured depending on the selected data pattern.
6. The USB test circuit in accordance with claim 5 , wherein said generation portion selects one of the data patterns for each one-bit data of the packet to be measured.
7. The USB test circuit in accordance with claim 1 , wherein said input portion serially receives the test signal from the external device.
8. The USB test circuit in accordance with claim 1 , wherein the USB device is fabricated in a form of system LSI (Large Scale Integration).