IDT72V805/72V815/72V825/72V835/72V845
3.3 V CMOS DUAL SyncFIFO 256 x 18, 512 x 18, 1,024 x 18, 4,096 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
3
FEBRUARY 11, 2009
PIN DESCRIPTION
Symbol
Name
I/O
Description
DA0–DA17
Data Inputs
I
Data inputs for an 18-bit bus.
DB0-DB17
RSA
Reset
I
When
RS is set LOW, internal read and write pointers are set to the first location of the RAM array, FF and
RSB
PAF go HIGH, and PAE and EF go LOW. A reset is required before an initial WRITE after power-up.
WCLKA
Write Clock
I
When
WEN is LOW, data is written into the FIFO on a LOW-to-HIGH transition of WCLK, if the FIFO is not full.
WCLKB
WENA
Write Enable
I
When
WEN is LOW, data is written into the FIFO on every LOW-to-HIGH transition of WCLK.
WENB
When
WEN is HIGH, the FIFO holds the previous data. Data will not be written into the FIFO if the FF is LOW.
RCLKA
Read Clock
I
When
REN is LOW, data is read from the FIFO on a LOW-to-HIGH transition of RCLK, if the FIFO is not
RCLKB
empty.
RENA
Read Enable
I
When
REN is LOW, data is read from the FIFO on every LOW-to-HIGH transition of RCLK. When REN
RENB
is HIGH, the output register holds the previous data. Data will not be read from the FIFO if the
EF is low.
OEA
Output Enable
I
When
OE is LOW, the data output bus is active. If OE is HIGH, the output data bus will be in a
OEB
high-impedance state.
LDA
Load
I
When
LD is LOW, data on the inputs D0–D11 is written to the offset and depth registers on the LOW-to-HIGH
LDB
transition of the WCLK, when
WEN is LOW. When LD is LOW, data on the outputs Q0–Q11 is read from the
offset and depth registers on the LOW-to-HIGH transition of the RCLK, when
REN is LOW.
FLA
First Load
I
In the single device or width expansion configuration,
FL together with WXI and RXI etermine if the mode is IDT
FLB
Standard mode or First Word Fall Through (FWFT) mode, as well as whether the
PAE/PAF flags are synchronous
or asynchronous. (See Table I.) In the Daisy Chain Depth Expansion configuration,
FL is grounded on the first
device (first load device) and set to HIGH for all other devices in the Daisy Chain.
WXIA
Write Expansion
I
In the single device or width expansion configuration,
WXI together with FL and RXI Input determine if the mode
WXIB
is IDT Standard mode or FWFT mode, as well as whether the
PAE/PAF flags are synchronous or asynchronous.
(See Table 1.) In the Daisy Chain Depth Expansion configuration,
WXI is connected to WXO (Write Expansion
Out) of the previous device.
RXIA
Read Expansion
I
In the single device or width expansion configuration,
RXI together with FL and WXI, Input determine if the mode
RXIB
is IDT Standard mode or FWFT mode, as well as whether the
PAE/PAF flags are synchronous or asynchronous.
(See Table 1.) In the Daisy Chain Depth Expansion configuration,
RXI is connected to RXO (Read
Expansion Out) of the previous device.
FFA/IRA
Full Flag/
O
In the IDT Standard mode, the
FF function is selected. FF indicates whether or not the FIFO memory is full.
FFB/IRB
Input Ready
In the FWFT mode, the
IR function is selected. IR indicates whether or not there is space available for writing to
the FIFO memory.
EFA/ORA
Empty Flag/
O
In the IDT Standard mode, the
EF function is selected. EF indicates whether or not the FIFO memory is
EFB/ORB
Output Ready
empty. In FWFT mode, the
OR function is selected. OR indicates whether or not there is valid data available at
the outputs.
PAEA
Programmable
O
When
PAE is LOW, the FIFO is almost-empty based on the offset programmed into the FIFO. The default offset
PAEB
Almost-Empty flag
at reset is 31 from empty for IDT72V805LB, 63 from empty for IDT72V815LB, and 127 from empty for IDT7V2825LB/
72V835LB/72V845LB.
PAFA
Programmable
O
When
PAF is LOW, the FIFO is almost-full based on the offset programmed into the FIFO. The default offset
PAFB
Almost-Full Flag
at reset is 31 from full for IDT72V805LB, 63 from full for IDT72V815LB, and 127 from full for IDT72V825LB/
72V835LB/72V845LB.
WXOA/HFA
Write Expansion
O
In the single device or width expansion configuration, the device is more than half full Out/Half-Full Flag
WXOB/
HFB
when
HF is LOW. In the depth expansion configuration, a pulse is sent from WXO to WXI of the next device
when the last location in the FIFO is written.
RXOA
Read Expansion
O
In the depth expansion configuration, a pulse is sent from
RXO to RXI of the next device when the last location
RXOB
Out
in the FIFO is read.
QA0–QA17
Data Outputs
O
Data outputs for an 18-bit bus.
QB0-QB17
VCC
Power
+3.3V power supply pins.
GND
Ground
Ground pins.