37

COMMERCIAL AND INDUSTRIAL

TEMPERATURE RANGES

IDT72T51333/72T51343/72T51353 2.5V, MULTI-QUEUE FLOW-CONTROL DEVICES

(8 QUEUES) 18 BIT WIDE CONFIGURATION 589,824, 1,179,648 and 2,359,296 bits

Figure 14. Output Valid Flag Timing (In Expansion Mode)

6113 drw18

*D*

*E*

*F*

*G*

*H*

*I*

*J*

RCLK

RADEN

RDADD

OV

(Device 1)

REN

Qout

(Device 1)

HIGH-Z

WCLK

OV

(Device 2)

WRADD

WADEN

Din

WEN

*A*

*B*

*C*

Addr=001011

Addr=001010

Addr=001010

Cycle:

*A* Queue 3 of Device 1 is selected for read operations. The

OV is currently being driven by Device 2, a queue within device 2 is selected for reads. Device 2 also has control

of Qout bus, its Qout outputs are in Low-Impedance. This diagram only shows the Qout outputs of device 1. (Reads are disabled).

*B* Reads are now enabled. A word from the previously selected queue of Device 2 will be read out.

*C* After a queue switch, there is a 3 RCLK latency for output data.

*D* The Qout of Device 1 goes to Low-Impedance and word Wd is read from Q3 of D1. This happens to be the last word of Q3. Device 2 places its Qout outputs into

High-Impedance, device 1 has control of the Qout bus. The

OV flag of Device 2 goes to High-Impedance and Device 1 takes control of OV. The OV flag of Device 1 goes LOW

to show that Wd of Q3 is valid.

*E* Queue 2 of device 1 is selected for read operations. The last word of Q3 was read on the previous cycle, therefore

OV goes HIGH to indicate that the data on the Qout is

not valid (Q3 was read to empty). Word, Wd remains on the output bus.

*F* The last word of Q3 remains on the Qout bus,

OV is HIGH, indicating that this word has been previously read.

*G* The next word (We-1), available from the newly selected queue, Q2 of device 1 is now read out. This will occur regardless of

REN, 2 RCLK cycles after queue selection

due to the FWFT operation. The

OV flag updates 3 RCLK cycles after a queue selection.

*H* The last word, We is read from Q2, this queue is now empty.

*I* The

OV flag goes HIGH to indicate that Q2 was read to empty on the previous cycle.

*J* Due to a write operation the