IDT72T55248

The IDT72T55248 QuadMux flow-control devices are ideal for many applications where data stream convergence and parallel buffering of multiple data paths are required. These applications may include communication and networking systems such as terabit routers, quality of service (QOS) and packet prioritization routing systems, data bandwidth aggregation, data acquisition systems, WCDMA baseband systems, and medical equipments. The QuadMux replaces traditional methods of muxing multiple data paths at different data rates, in essence reducing external glue logic. The QuadMux offers three modes of operation, Mux, Demux and Broadcast. Regardless of the mode of operation there are four internal Sequential Queues built using IDT FIFO technology and five discrete clock domains. All four Queues have the same density, and the read and write ports can operate independently in Single Data Rate (SDR) or Double Data Rate (DDR). See Figure 1, QuadMux Block Diagram or an outline of the functional blocks within the device.

The QuadMux device of the IDT72T55248 is capable of up to 200MHz operation of all five clock inputs, all clocks being totally independent of each other. Along with this high speed of operation the input and output ports are independently selectable between Single Data Rate, SDR mode, and Double Data Rate, DDR mode. If Double Data Rate mode is selected data can be written into or read out of a Queue on every rising and falling edge of the respective clock. For example, if the write clock is running at 200MHz and the write port(s) is/are setup for DDR mode, a data input pin has a bandwidth of 400Mbps. So for a 40-bit wide bus a total bandwidth of 16Gbps can be achieved.

In Mux mode operation a 4:1 architecture of the IDT72T55248 is setup, (four input ports to one output port). Here there are four internal Sequential Queues each with a dedicated write port. Data can be written into each of the dedicated write ports totally independent of any other port, each port has its own write clock input and control enables. There is a single read port that can access any one of the four Queues. Data is read out of a specific Queue based on the address present on the output select pins. Only one Queue can be selected and read from at a time. All input ports are 10 bits wide and the output port has a selectable Bus Matching x10, x20 or x40 bus widths. A full set of flag outputs per Queue are available in this mode providing the user with continuous status of each individual Queue levels.

In Demux mode operation a 1:4 architecture of the IDT72T55248 is setup, (one input port to four output ports). Here there is a single write port that can write data into any one of four internal Queues. Data is written into a specific Queue based on the address present on the input select pins. Only one Queue can be selected and written into at a time. There are four dedicated read ports, one port for each Queue. Data can be read out of the four Queues through the read port totally independent of any other port. Each port has its own read clock input and control enables. The input port has a selectable Bus Matching x10, x20 or x40 bus width and all the output ports are 10-bits. A full set of flag outputs per Queue are available in this mode providing the user with continuous status of each individual Queue levels.

In the Broadcast Write mode the architecture of the IDT72T55248 is similar to the Demux mode, 1:4 (one input port to four output ports). However, there is no Queue select operation in Broadcast mode. Instead data written into the write port is written to all four internal Queues simultaneously. Again there are four independent read ports, one port per Queue. In Broadcast mode write operations to all Queues will be prevented when any one or more of the four Queues are full or being partially reset. A full set of flag outputs is available in this mode providing the user with continuous status of each individual Queue levels.

As is typical with most IDT Queues of the IDT72T55248, two types of data timing modes are available, IDT Standard mode and First Word Fall Through (FWFT) mode. This affects the device's operation and also the flag outputs. The device provides four flag outputs, for each internal Queue. The device also provides composite flags that represent the full and empty status of the currently selected Queue.

All read ports provide the user with a dedicated Echo Read Enable of the IDT72T55248, EREN and an Echo Read Clock, ERCLK output. These outputs aid in high-speed applications where synchronization of the input clock and data of a receiving device is critical. Otherwise known as "Source Synchronous clocking" the echo outputs provide tighter synchronization of the data transmitted from the Queue to the read clock interfacing the Queue outputs.

A master reset input of the IDT72T55248 is provided and all setup and configuration pins are latched with respect to a Master Reset. A Partial Reset is provided for each internal Queue. When a Partial Reset is performed on a Queue the read and write pointers of that Queue only are reset to the first memory location. The flag offset values, timing modes, and initial configurations are retained.

The QuadMux device of the IDT72T55248 has the capability of operating its I/Os at either 2.5V LVTTL, 1.5V HSTL or 1.8V eHSTL levels. A Voltage Reference, VREF input is provided for HSTL and eHSTL interfaces. The type of I/O is selected by the IOSEL pin. There are certain inputs that are CMOS based and must be tied to either VCC or GND. The core supply voltage of the device, VCC is always 2.5V, however the output pins have a separate supply, VDDQ which can be 2.5V, 1.8V or 1.5V. The device also offers significant power savings, achieved through the use of the Power Down input, PD in HSTL/eHSTL mode.

A JTAG test port of the IDT72T55248 is provided on the QuadMux device. The Boundary Scan is fully compliant with IEEE 1149.1 Standard Test Access Port and Boundary Scan Architecture. The JTAG port can also be used to program the flag offsets.