IDT7207(1996) 查看數據表（PDF） - Integrated Device Technology

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IDT7207
(Rev.:1996)

CMOS ASYNCHRONOUS FIFO 32,768 x 9

Integrated Device Technology 

IDT7207 CMOS ASYNCHRONOUS FIFO

32,768 x 9

t XI

t XIR

MILITARY AND COMMERCIAL TEMPERATURE RANGES

XI

t XIS

WRITE TO

FIRST PHYSICAL

W

LOCATION

R

t XIS

READ FROM

FIRST PHYSICAL

LOCATION

Figure 11. Expansion In

3140 drw 14

OPERATING MODES:

Care must be taken to assure that the appropriate flag is

monitored by each system (i.e. FF is monitored on the device

where W is used; EF is monitored on the device where R is

used). For additional information, refer to Tech Note 8: Oper-

ating FIFOs on Full and Empty Boundary Conditions and

Tech Note 6: Designing with FIFOs.

Single Device Mode

A single IDT7207 may be used when the application

requirements are for 32,768 words or less. The IDT7207 is

in a Single Device Configuration when the Expansion In (XI)

control input is grounded (see Figure 12).

Depth Expansion

The IDT7207 can easily be adapted to applications when

the requirements are for greater than 32,768 words. Figure 14

demonstrates Depth Expansion using three IDT7207s. Any

depth can be attained by adding additional IDT7207s. The

IDT7207 operates in the Depth Expansion mode when the

following conditions are met:

1. The first device must be designated by grounding the First

Load (FL) control input.

2. All other devices must have FL in the HIGH state.

3. The Expansion Out (XO) pin of each device must be tied to

the Expansion In (XI) pin of the next device. See Figure 14.

4. External logic is needed to generate a composite Full Flag

(FF) and Empty Flag (EF). This requires the ORing of all

EFs and ORing of all FFs (i.e. all must be set to generate the

correct composite FF or EF). See Figure 14.

5. The Retransmit (RT) function and Half-Full Flag (HF) are

not available in the Depth Expansion Mode.

For additional information, refer to Tech Note 9: Cascading

FIFOs or FIFO Modules.

USAGE MODES:

corresponding input control signals of multiple devices. Sta-

tus flags (EF, FF and HF) can be detected from any one device.

Figure 13 demonstrates an 18-bit word width by using two

IDT7207s. Any word width can be attained by adding addi-

tional IDT7207s (Figure 13).

Bidirectional Operation

Applications which require data buffering between two

systems (each system capable of Read and Write operations)

can be achieved by pairing IDT7207s as shown in Figure 16.

Both Depth Expansion and Width Expansion may be used in

this mode.

Data Flow-Through

Two types of flow-through modes are permitted, a read

flow-through and write flow-through mode. For the read flow-

through mode (Figure 17), the FIFO permits a reading of a

single word after writing one word of data into an empty FIFO.

The data is enabled on the bus in (tWEF + tA) ns after the rising

edge of W, called the first write edge, and it remains on the bus

until the R line is raised from LOW-to-HIGH, after which the

bus would go into a three-state mode after tRHZ ns. The EF line

would have a pulse showing temporary deassertion and then

would be asserted.

In the write flow-through mode (Figure 18), the FIFO

permits the writing of a single word of data immediately after

reading one word of data from a full FIFO. The R line causes

the FF to be deasserted but the W line being LOW causes it to

be asserted again in anticipation of a new data word. On the

rising edge of W, the new word is loaded in the FIFO. The W

line must be toggled when FF is not asserted to write new data

in the FIFO and to increment the write pointer.

Compound Expansion

The two expansion techniques described above can be

applied together in a straightforward manner to achieve large

FIFO arrays (see Figure 15).

Width Expansion

Word width may be increased simply by connecting the

5.05

8

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