14
IDT72205LB/72215LB/72225LB/72235LB/72245LB CMOS SyncFIFO
TM
256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
MARCH 2013
OPERATING CONFIGURATIONS
SINGLE DEVICE CONFIGURATION
A single IDT
72205LB/72215LB/72225LB/72235LB/72245LB may be used
when the application requirements are for 256/512/1,024/2,048/4,096 words
or less. These FIFOs are in a single Device Configuration when the First Load
(FL), Write Expansion In (WXI) and Read Expansion In (RXI) control inputs
are grounded (Figure 19).
Figure 19. Block Diagram of Single 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18, 4,096 x 18 Synchronous FIFO
NOTE:
1. Do not connect any output control signals directly together.
Figure 20. Block Diagram of 256 x 36, 512 x 36, 1,024 x 36, 2,048 x 36, 4,096 x 36
Synchronous FIFO Memory Used in a Width Expansion Configuration
WIDTH EXPANSION CONFIGURATION
Word width may be increased simply by connecting together the control
signals of multiple devices. Status flags can be detected from any one device.
The exceptions are the Empty Flag and Full Flag. Because of variations in skew
between RCLK and WCLK, it is possible for flag assertion and deassertion to
vary by one cycle between FIFOs. To avoid problems the user must create
composite flags by ANDing the Empty Flags of every FIFO, and separately
ANDing all Full Flags. Figure 20 demonstrates a 36-word width by using two
IDT72205LB/72215LB/72225LB/72235LB/72245LBs. Any word width can
be attained by adding additional IDT72205LB/72215LB/72225LB/72235LB/
72245LBs. Please see the Application Note AN-83.
WRITE CLOCK (WCLK)
WRITE ENABLE (WEN)
READ CLOCK (RCLK)
READ ENABLE (REN)
LOAD (LD)
OUTPUT ENABLE (OE)
DATA IN (D)
DATA OUT (Q)
FULL FLAG (FF)
PROGRAMMABLE (PAE)
HALF FULL FLAG (HF)
EMPTY FLAG (EF)
PROGRAMMABLE (PAF)
RESET (RS)
72205LB
72215LB
72225LB
72235LB
72245LB
72205LB
72215LB
72225LB
72235LB
72245LB
RESET (RS)
36
36
18 18
18
18
FF FF EFEF
2766 drw 22
FIRST LOAD (FL)
READ EXPANSION IN (RXI)
WRITE EXPANSION IN (WXI)
WRITE CLOCK (WCLK)
WRITE ENABLE (
)
READ CLOCK (RCLK)
READ ENABLE (
)
LOAD (
)
OUTPUT ENABLE (
)
DATA IN (D
0
- D
17
)
DATA OUT (Q
0
- Q
17
)
FULL FLAG (
)
PROGRAMMABLE (
)
HALF-FULL FLAG (
)
EMPTY FLAG (
)
PROGRAMMABLE (
)
RESET (
)
IDT
72205LB
72215LB
72225LB
72235LB
72245LB
2766 drw 21
FIRST LOAD ( )
READ EXPANSION IN (
)
WRITE EXPANSION IN (
)
