IDT72V3642

The IDT72V3622/72V3632/72V3642 are functionally compatible versions of the IDT723622/723632/723642, designed to run off a 3.3V supply for exceptionally low-power consumption. These devices are monolithic, highspeed, low-power, CMOS Bidirectional SyncFIFO (clocked) memories which support clock frequencies up to 100MHz and have read access times as fast as 6.5ns. Two independent 256/512/1,024 x 36 dual-port SRAM FIFOs on board each chip buffer data in opposite directions. Communication between each port may bypass the FIFOs via two 36-bit mailbox registers. Each mailbox register has a flag to signal when new mail has been stored.

These devices are a synchronous (clocked) FIFO, meaning each port employs a synchronous interface. All data transfers through a port are gated to the LOW-to-HIGH transition of a port clock by enable signals. The clocks for each port are independent of one another and can be asynchronous or coincident. The enables for each port are arranged to provide a simple bidirectional interface between microprocessors and/or buses with synchronous control.

These devices have two modes of operation: In the IDT Standard mode, the first word written to an empty FIFO is deposited into the memory array. A read operation is required to access that word (along with all other words residing in memory). In the First Word Fall Through mode (FWFT), the first long-word (36-bit wide) written to an empty FIFO appears automatically on the outputs, no read operation required (Nevertheless, accessing subsequent words does necessitate a formal read request). The state of the FWFT pin during FIFO operation determines the mode in use.

Each FIFO has a combined Empty/Output Ready Flag (EFA/ORA and EFB/ORB) and a combined Full/Input Ready Flag (FFA/IRA and FFB/IRB). The EF and FF functions are selected in the IDT Standard mode. EF indicates whether or not the FIFO memory is empty. FF shows whether the memory is full or not. The IR and OR functions are selected in the First Word Fall Through mode. IR indicates whether or not the FIFO has available memory locations. OR shows whether the FIFO has data available for reading or not. It marks the presence of valid data on the outputs.

Each FIFO has a programmable Almost-Empty flag (AEA and AEB) and a programmable Almost-Full flag (AFA and AFB). AEA and AEB indicate when a selected number of words remain in the FIFO memory. AFA and AFBindicate when the FIFO contains more than a selected number of words.

FFA/IRA, FFB/IRB, AFA and AFB are two-stage synchronized to the port clock that writes data into its array. EFA/ORA,EFB/ORB, AEA and AEB are two-stage synchronized to the port clock that reads data from its array. Programmable offsets for AEA, AEB, AFA andAFB are loaded by using Port A. Three default offset settings are also provided. The AEA and AEB threshold can be set at 8, 16 or 64 locations from the empty boundary and the AFA and AFB threshold can be set at 8, 16 or 64 locations from the full boundary. All these choices are made using the FS0 and FS1 inputs during Reset.

Two or more devices may be used in parallel to create wider data paths. If, at any time, the FIFO is not actively performing a function, the chip will automatically power down. During the power down state, supply current consumption (I_CC) is at a minimum. Initiating any operation (by activating control inputs) will immediately take the device out of the power down state.

The IDT72V3622/72V3632/72V3642 are characterized for operation from 0oC to 70oC. Industrial temperature range (-40C to +85C) is available by special order. They are fabricated using IDT's high speed, submicron CMOS technology.