ARRANGEMENT FOR CONVERTING BETWEEN A REDUCED MEDIA INDEPENDENT INTERFACE DATA STREAM AND A MEDIA INDEPENDENT INTERFACE DATA STREAM

Abstract: A conversion device is configured for converting reduced media independent interface signals into media independent interface signals, and media independent interface signals into reduced media independent interface signals. Hence, a device under test, for example an integrated network switch utilizing a reduced media independent interface, can be tested by test equipment configured for sending and receiving data packets across a media independent interface using the conversion device to convert between the two interfaces.

Description: ARRANGEMENT FOR CONVERTING BETWEEN A REDUCED MEDIA INDEPENDENT INTERFACE DATA STREAM AND A MEDIA INDEPENDENT INTERFACE DATA STREAM FIELD OF THE INVENTION The present invention relates to testing of integrated network devices such as integrated network switches configured for switching data packets between subnetworks. BACKGROUND ART Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface devices at each network node to access the network medium. Switched local area networks are encountering increasing demands for higher speed connectivity, more flexible switching performance, and the ability to accommodate more complex network architectures. For example, commonly-assigned U.S. Patent No. 5,953,335 discloses a network switch configured for switching layer 2 type Ethernet (IEEE 802.3) data packets between different network nodes; a received layer 2 type data packet may include a VLAN (virtual LAN) tagged frame according to IEEE 802.1p (802.1D) protocol that enables the network switch to perform more advanced switching operations. For example, the VLAN tag may specify another subnetwork (via a router) or a prescribed group of stations. A particular concern in testing high-performance integrated network switches implemented on a single chip is incompatibility of existing test equipment with newer switch designs. For example, newer devices reduce pin count by utilizing a Reduced Media Independent Interface (RMII), published by the RMII Consortium. The RMII utilizies six (6) pins per port and one pin per switch ASIC, as opposed to a conventional Media Independent Interface (Mil) specified by IEEE 802.3u[2] as having sixteen (16) pins per port, enabling the pin count for integrated multiple port devices such as switches, hubs, repeaters, etc. to be substantially reduced. Hence, existing test equipment having only an Mil interface for connecting devices under test currently are unusable for testing newer integrated devices having RMII interfaces. Hence, a test designer is unable to test the device, for example by sending and receiving test packets, to verify operation ofthe device under test. • SUMMARY OF THE INVENTION There is a need for an arrangement that enables a data stream to be converted between an Mil interface and an RMII interface for flexibility in testing an integrated network device having an interface that is not compatible with a test device. These and other needs are attained by the present invention, where a conversion device is configured for converting reduced media independent interface signals into media independent interface signals, and media independent interface signals into reduced media independent interface signals. Hence, a device under test, for example an integrated network switch utilizing a reduced media independent interface, can be tested by test equipment configured for sending and receiving data packets across a media independent interface using the conversion device to convert between the two interfaces. One aspect of the present invention provides a method for converting data streams. The method includes receiving a first data stream from a media access controller according to a reduced media independent interface protocol, converting the first data stream to a second data stream compliant with a media independent interface protocol, and outputting the second data stream and media independent interface control signals according to the media independent interface protocol. Outputting the second data stream and media independent interface (Mil) control signals based on the first data stream provides compatibility between conventional Mil devices and newer integrated network devices utilizing newer reduced media independent interface (RMII) protocols to reduce pin count. Hence, newer integrated network devices utilizing the RMII protocol can be connected to older devices utilizing a conventional MI, for example test devices or conventional physical layer transceivers. Another aspect of the present invention provides an apparatus configured for converting a reduced media independent interface protocol and a media independent interface protocol. The apparatus includes a reduced media independent interface configured for receiving a transmit data stream according to a reduced media independent interface protocol, logic configured for converting the transmit data stream to a modified transmit data stream compliant with a media independent interface protocol, and a media independent interface configured for outputting the modified transmit data stream according to the media independent interface protocol. Additional advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the present invention may be realized and attained by means of instrumentalities and combinations particularly pointed in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Reference is made to the attached drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: Figure 1 is a block diagram of a system configured for converting an RMII data stream from a device under test, for example an integrated network switch, into an Mil data stream for use by an Mil based device. Figures 2A and 2B are diagrams summarizing the method of converting between an RMII data stream and an Mil data stream according to an embodiment ofthe present invention. BEST MODE FOR CARRYING OUT THE INVENTION Figure 1 is a block diagram illustrating a testing system configured for testing an integrated (i.e., single chip) network device 10, for example a multiport switch having switch ports that include a media access controller (MAC), enabling transmission and reception of layer 2 type data packets between network stations at 10 or 100 Mbps according to a reduced media independent interface protocol. In particular, the network device 10, also referred to as the device under test (DUT), includes an RMII interface 12a for transmission and reception of transmit and receive data streams according to the RMII specification published by the RMII Consortium. In particular, the RMII interface 12 includes a 2-bit receive data path (RXD), a carrier sense/data valid signal (CRS_DV), a clock signal (REF_CLK), a 2-bit transmit data path (TXD), and a transmit enable signal (TX_EN). The testing system also includes test equipment 14 (or a physical layer transceiver) having a media independent interface 16a for transmission and reception of transmit and receive data streams according to the ME protocol specified by IEEE 802.3u[2]. In particular, the Mil includes a 4-bit receive data path (RXD), a carrier sense signal (CRS), a receive data valid signal (RX_DV), a receive error signal (RX_ER), a receive clock signal (RX_CLK), a 4-bit transmit data path (TXD), a transmit enable signal (TXJEN), a transmit error signal (TX_ER), and a transmit clock (TX_CLK). As described above, the differences between the RMII interface and the Mil interface prevent the RMII interface 12a ofthe device under test 10 from being directly connected to the Mil interface 16a of the test equipment 14. However, products such as the device under test 10 need to be rapidly tested as they are being developed to minimize delays in introducing the device under test 10 to market. Hence, the acquisition of test devices having RMTJ interfaces may be unacceptably costly and may cause substantial delays in the testing process. According to the disclosed embodiment, a converter 20 is configured for converting between the RMII interface 12a and the MQ interfacelόa, enabling interoperability between the RMH-based device under test 10 and the MH-based test equipment 14. The converter 20, implemented for example using a field programmable gate array (FPGA), includes an RMTI interface 12b configured for sending and receiving the RMII signals between the device under test 10, an Mil interface 16b configured for sending and receiving the Mil signals between the test equipment 14, and conversion logic 22. The conversion logic 22 includes a first logic block 22a configured for converting the ME signals into RMII signals, and a second logic block 22b configured for converting the RMII signals into Mil signals. Each logic block 22 includes data conversion logic 24 and control signal conversion logic 26 for converting the data signals and the control signals, respectively. Although the conversion logic 22a is illustrated as converting Mil receive data (RXD) into RMII receive data (RXD) and the conversion logic 22b is illustrated as converting RMII transmit data (TXD) into Mil transmit data (TXD), additional logic can be added to provide symmetrical conversion, such that the converter 20 also can convert Mil transmit data (TXD) and RMII receive data (RXD). The RMII and Mil data streams are converted using an RMII clock (REF_CLK) that is at least twice the frequency ofthe Mil clocks (TX_CLK or RX_CLK). For example, if the Mil clock rate runs at a maximum rate of 100 Mbps (25 MHz), the RMII clock runs at 50 MHz. However if the Mil runs at 10 Mbps or 2.5 MHz, the RMII clock can be divided by 20 to obtain the 10 Mbps data rate. Figures 2A and 2B are diagrams summarizing the method of converting between the RMII and Mil data streams according to an embodiment of the present invention. Conversion of the 2-bit RMII transmit data stream (TXD) begins in step 50 of Figure 2A by the conversion logic 22b receiving the RMII data signals (TXD), the RMII clock (REF_CLK), and the RMII control signal (TX_EN) in step 50. The data conversion logic 24b converts the 2-bit transmit data path based on the 50 MHz clock into a 4-bit 100 Mb/s transmit data path in step 52. The control signal conversion logic 26b converts ("reflects") the RMII control signal to the ME control signals in step 54, according to the ME and RMII specifications, and the ME interface 16b outputs the converted ME signals in step 56. Conversion of the 4-bit ME receive data stream (RXD) begins in step 60 of Figure 2B by the conversion logic 22a receiving the ME data signals (RXD), the Mil clock (RX_CLK), and the ME control signals (CRS, RX_DV, RX_ER). The data conversion logic 24a converts the 4-bit receive data path (RXD) into the 2-bit RMII data stream (RXD) in step 62. The control signal conversion logic 26a converts ("reflects") the MB control signals to the RMH control signal (CRS_DV) in step 64, and the RME interface 12b outputs the RMII control and data signals according to the RMII clock in step 66. According to the disclosed embodiment, data streams are converted between the RMII interface protocol and the ME interface protocol, enabling integrated devices to be tested using test equipment having different media interfaces, reducing compatibility problems associated with testing newer interfaces using existing testing equipment. While this invention has been described with what is presently considered to be the most practical preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope ofthe appended claims.

Claims: What is Claimed Is: 1. A method comprising: receiving a first data stream from a media access controller according to a reduced media independent interface protocol; converting the first data stream to a second data stream compliant with a media independent interface protocol; and outputting the second data stream and media independent interface control signals according to the media independent interface protocol. 2. The method of claim 1, wherein the receiving step includes receiving a 2-bit transmit data stream as the first data stream from the media access controller, the converting step including converting the 2-bit transmit data stream into a 4-bit transmit data stream as the second data stream. 3. The method of claim 2, wherein the outputting step includes generating the media independent interface control signals based on reception of reduced media independent interface control signals from the media access controller. 4. The method of claim 3, wherein the converting step and the outputting step are performed by a field programmable gate array. 5. The method of claim 3, wherein the generating step includes generating a clock for the media independent interface having a prescribed frequency based on reception of a reduced media independent interface reference clock having twice the prescribed frequency ofthe clock for the media independent interface. 6. The method of claim 3, wherein the step of generating a clock includes generating the clock at one of 2.5 MHz and 25 MHz as the prescribed frequency based on the reduced media independent interface reference clock having a rate of 50 MHz. 7. The method of claim 2, further comprising: receiving a third 4-bit data stream according to the media independent interface protocol; converting the third 4-bit data stream into a fourth 2-bit data stream compliant with the reduced media independent interface protocol; and outputting the fourth 2-bit data stream to the media access controller according to the reduced media independent interface protocol. 8. An apparatus comprising: a reduced media independent interface configured for receiving a transmit data stream according to a reduced media independent interface protocol; logic configured for converting the transmit data stream to a modified transmit data stream compliant with a media independent interface protocol; and a media independent interface configured for outputting the modified transmit data stream according to the media independent interface protocol. 9. The apparatus of claim 8, wherein the logic includes control signal logic configured for generating media independent interface transmit control signals based on reception of reduced media independent interface transmit control signals. 10. The apparatus of claim 9, wherein the logic is configured for converting a receive data stream, received from the media independent interface, into a modified receive data stream according to the reduced media independent interface protocol, the control signal logic configured for generating at least one reduced media independent interface control signal based on media independent interface control signals.

Inventors: COOPER MELISSA, STERNER RUDOLPH J, COOPER, MELISSA, STERNER, RUDOLPH, J.
Applicants: ADVANCED MICRO DEVICES INC, ADVANCED MICRO DEVICES, INC.
Application year: 2001
Main classification: H04L29
IPC codes: H04L12, H04L29