3.3 VOLT CMOS SyncFIFO
TM
WITH BUS-MATCHING
256 x 36, 512 x 36, 1,024 x 36
FEATURES:
• Memory storage capacity:
IDT72V3623–256 x 36
IDT72V3633–512 x 36
IDT72V3643–1,024 x 36
• Clock frequencies up to 83 MHz (8 ns access time)
• Clocked FIFO buffering data from Port A to Port B
FF)
• IDT Standard timing (using
EF
and
FF
or First Word Fall
Through Timing (using OR and IR flag functions)
• Programmable Almost-Empty and Almost-Full flags; each has
three default offsets (8, 16 and 64)
• Serial or parallel programming of partial flags
• Port B bus sizing of 36 bits (long word), 18 bits (word) and 9 bits
(byte)
PRELIMINARY
IDT72V3623
IDT72V3633
IDT72V3643
• Big- or Little-Endian format for word and byte bus sizes
• Reset clears data and configures FIFO, Partial Reset clears data
but retains configuration settings
• Mailbox bypass registers for each FIFO
• Free-running CLKA and CLKB may be asynchronous or
coincident (simultaneous reading and writing of data on a single
clock edge is permitted)
• Easily expandable in width and depth
• Auto power down minimizes power dissipation
• Available in a space-saving 128-pin Thin Quad Flatpack (TQFP)
• Pin and functionally compatible versions of the 5V operating
IDT723623/723633/723643
• Industrial temperature range (–40
o
C to +85
o
C) is available
FUNCTIONAL BLOCK DIAGRAM
MBF1
Mail 1
Register
Port-A
Control
Logic
Bus-
Matching
Input
Register
Output
Register
36
CLKA
CSA
W/RA
ENA
MBA
RS1
RS2
PRS
RAM ARRAY
36
FIFO1
Mail1,
Mail2,
Reset
Logic
36
256 x 36
512 x 36
1,024 x 36
36
A
0
-A
35
Write
Pointer
Read
Pointer
B
0
-B
35
FF/IR
AF
Status Flag
Logic
EF/OR
AE
36
36
SPM
FS0/SD
FS1/SEN
Programmable Flag
Offset Registers
9
Timing
Mode
Port-B
Control
Logic
Mail 2
Register
MBF2
FWFT
CLKB
CSB
W/RB
ENB
MBB
BE
BM
SIZE
4662 drw 01
June 1999
1
©
1999
Integrated Device Technology, Inc.
DSC-4662/-
IDT72V3623/33/43
IDT
fast as 8 ns. The 256/512/1,024 x 36 dual-port SRAM FIFO buffers data from
Port A to Port B. FIFO data on Port B can output in 36-bit, 18-bit, or 9-bit formats
with a choice of Big- or Little-Endian configurations.
These devices are synchronous (clocked) FIFOs, 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
DESCRIPTION:
The IDT72V3623/72V3633/72V3643 are pin and functionally compatible
versions of the IDT723623/723633/723643, designed to run off a 3.3V supply
for exceptionally low power consumption. These devices are monolithic, high-
speed, low-power, CMOS unidirectional Synchronous (clocked) FIFO memory
which supports clock frequencies up to 83 MHz and has read access times as
PIN CONFIGURATION
CSA
FF/IR
NC
PRS
Vcc
AF
NC
MBF2
MBA
RS1
FS0/SD
GND
GND
FS1/SEN
RS2
MBB
MBF1
Vcc
AE
NC
EF/OR
NC
GND
CSB
W/RB
ENB
INDEX
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
W/RA
ENA
CLKA
GND
A35
A34
A33
A32
Vcc
A31
A30
GND
A29
A28
A27
A26
A25
A24
A23
BE/FWFT
GND
A22
Vcc
A21
A20
A19
A18
GND
A17
A16
A15
A14
A13
Vcc
A12
GND
A11
A10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
128
127
126
125
124
123
122
121
120
119
118
117
116
115
114
113
112
111
110
109
108
107
106
105
104
103
102
101
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
CLKB
Vcc
Vcc
B35
B34
B33
B32
GND
GND
B31
B30
B29
B28
B27
B26
Vcc
B25
B24
BM
GND
B23
B22
B21
B20
B19
B18
GND
B17
B16
SIZE
Vcc
B15
B14
B13
B12
GND
B11
B10
A9
A8
A7
A6
GND
A5
A4
A3
SPM
Vcc
A2
A1
A0
GND
B0
B1
B2
B3
B4
B5
GND
B6
Vcc
B7
B8
B9
4662 drw 02
TQFP (PK128-1, order code: PF)
TOP VIEW
2
IDT72V3623/33/43
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 synchro-
nous control.
Communication between each port may bypass the FIFO via two mailbox
registers. The mailbox registers' width matches the selected Port B bus width.
Each mailbox register has a flag (MBF1 and
MBF2)
to signal when new mail
has been stored.
Two kinds of reset are available on these FIFOs: Reset and Partial Reset.
Reset initializes the read and write pointers to the first location of the memory array
and selects serial flag programming, parallel flag programming, or one of three
possible default flag offset settings, 8, 16 or 64.
Partial Reset also sets the read and write pointers to the first location of the
memory. Unlike Reset, any settings existing prior to Partial Reset (i.e.,
programming method and partial flag default offsets) are retained. Partial Reset
is useful since it permits flushing of the FIFO memory without changing any
configuration settings.
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
word written to an empty FIFO appears automatically on the outputs, no read
operation required (Nevertheless, accessing subsequent words does neces-
sitate a formal read request). The state of the BE/FWFT pin during Reset
determines the mode in use.
The FIFO has a combined Empty/Output Ready Flag (EF/OR ) and a
combined Full/Input Ready Flag (FF/IR). 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
IDT
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.
The FIFO has a programmable Almost-Empty flag (AE) and a program-
mable Almost-Full flag (AF).
AE
indicates when a selected number of words
remain in the FIFO memory.
AF
indicates when the FIFO contains more than
a selected number of words.
FF/IR
and
AF
are two-stage synchronized to the port clock that writes data
into its array.
EF/OR
and
AE
are two-stage synchronized to the port clock that
reads data from its array. Programmable offsets for
AE
and
AF
are loaded in
parallel using Port A or in serial via the SD input. The Serial Programming Mode
pin (SPM) makes this selection. Three default offset settings are also provided.
The
AE
threshold can be set at 8, 16 or 64 locations from the empty boundary
and the
AF
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.
In First Word Fall Through mode, more than one device may be connected in
series to create greater word depths. The addition of external components is
unnecessary.
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 IDT72V3623/72V3633/72V3643 are characterized for operation from
o
0 C to 70
o
C. Industrial temperature range (-40
o
C to +85
o
C) is available by
special order. They are fabricated using IDT’s high speed, submicron CMOS
technology.
3
IDT72V3623/33/43
IDT
PIN DESCRIPTIONS
Symbol
A0-A35
AE
AF
B0-B35
BE/FWFT
Name
Port A Data
Almost-Empty Flag
(Port B)
Almost-Full Flag
(Port A)
Port B Data
Big-Endian/
First Word
Fall Through
I/O
I/O
O
O
I/O
I
36-bit bidirectional data port for side A.
Programmable Almost-Empty flag synchronized to CLKB. It is LOW when the number of words in
the FIFO is less than or equal to the value in the Almost-Empty B offset register, X.
Programmable Almost-Full flag synchronized to CLKA. It is LOW when the number of empty
locations in the FIFO is less than or equal to the value in the Almost-Full A offset register, Y.
36-bit bidirectional data port for side B.
This is a dual purpose pin. During Master Reset, a HIGH on BE will select Big-Endian operation.
In this case, depending on the bus size, the most significant byte or word written to Port A is read
from Port B first. A LOW on BE will select Little-Endian operation. In this case, the least significant
byte or word written to Port A is read from Port B first. After Master Reset, this pin selects the timing
mode. A HIGH on
FWFT
selects IDT Standard mode, a LOW selects First Word Fall Through
mode. Once the timing mode has been selected, the level on
FWFT
must be static throughout
device operation.
A HIGH on this pin enables either byte or word bus width on Port B, depending on the state of
SIZE. A LOW selects long word operation. BM works with SIZE and BE to select the bus size and
endian arrangement for Port B. The level of BM must be static throughout device operation.
CLKA is a continuous clock that synchronizes all data transfers through Port A and can be
asynchronous or coincident to CLKB.
FF/IR
and
AF
are synchronized to the LOW-to-HIGH
transition of CLKA.
CLKB is a continuous clock that synchronizes all data transfers through Port B and can be
asynchronous or coincident to CLKA.
EF/OR
and
AE
are synchronized to the LOW-to-HIGH
transition of CLKB.
CSA
must be LOW to enable to LOW-to-HIGH transition of CLKA to read or write on Port A. The
A0-A35 outputs are in the high-impedance state when
CSA
is HIGH.
CSB
must be LOW to enable a LOW-to-HIGH transition of CLKB to read or write data on Port B.
The B0-B35 outputs are in the high-impedance state when
CSB
is HIGH.
This is a dual function pin. In the IDT Standard mode, the
EF
function is selected.
EF
indicates
whether or not the FIFO memory is empty. In the FWFT mode, the OR function is selected. OR indicates
the presence of valid data on the B0-B35 outputs, available for reading.
EF/OR
is synchronized to the
LOW-to-HIGH transition of CLKB.
ENA must be HIGH to enable a LOW-to-HIGH transition of CLKA to read or write data on Port A.
ENB must be HIGH to enable a LOW-to-HIGH transition of CLKB to read or write data on Port B.
This is a dual function pin. In the IDT Standard mode, the
FF
function is selected.
FF
indicates
whether or not the FIFO memory is full. In the FWFT mode, the IR function is selected. IR
indicates whether or not there is space available for writing to the FIFO memory.
FF/IR
is
synchronized to the LOW-to-HIGH transition of CLKA.
I
FS1/SEN and FS0/SD are dual-purpose inputs used for flag offset register programming. During
Reset, FS1/SEN and FS0/SD, together with
SPM,
select the flag offset programming method.
Three offset register programming methods are available: automatically load one of three preset
values (8, 16, or 64), parallel load from Port A, and serial load.
When serial load is selected for flag offset register programming, FS1/SEN is used as an enable
synchronous to the LOW-to-HIGH transition of CLKA. When FS1/SEN is LOW, a rising edge on
CLKA load the bit present on FS0/SD into the X and Y registers. The number of bit writes required
to program the offset registers is 16 for the 72V3623, 18 for the 72V3633, and 20 for the 72V3643.
The first bit write stores the Y-register MSB and the last bit write stores the X-register LSB.
Description
BM
Bus-Match Select
(Port B)
Port A Clock
I
CLKA
I
CLKB
Port B Clock
I
CSA
CSB
EF/OR
Port A Chip
Select
Port B Chip
Select
Empty/Output
Ready Flag
(Port B)
Port A Enable
Port B Enable
Full/Input
Ready Flag
(Port A)
Flag Offset
Select 1/
Serial Enable,
Flag Offset
Select 0/
Serial Data
I
I
O
ENA
ENB
FF/IR
I
I
O
FS1/SEN
FS0/SD
I
4
IDT72V3623/33/43
IDT
PIN DESCRIPTIONS (Continued)
Symbol
MBA
MBB
Name
Port A Mailbox
Select
Port B Mailbox
Select
Mail1 Register Flag
I/O
I
I
Description
A HIGH level on MBA chooses a mailbox register for a Port A read or write operation.
A HIGH level on MBB chooses a mailbox register for a Port B read or write operation. When the
B0-B35 outputs are active, a HIGH level on MBB selects data from the mail1 register for output and
a LOW level selects FIFO data for output.
MBF1
is set LOW by a LOW-to-HIGH transition of CLKA that writes data to the mail1 register.
Writes to the mail1 register are inhibited while
MBF1
is LOW.
MBF1
is set HIGH by a LOW-to-
HIGH transition of CLKB when a Port B read is selected and MBB is HIGH.
MBF1
is set HIGH
following either a Reset (RS1) or Partial Reset (PRS).
MBF2
is set LOW by a LOW-to-HIGH transition of CLKB that writes data to the mail2 register.
Writes to the mail2 register are inhibited while
MBF2
is LOW.
MBF2
is set HIGH by a LOW-to-
HIGH transition of CLKA when a Port A read is selected and MBA is HIGH.
MBF2
is set HIGH
following either a Reset (RS2) or Partial Reset (PRS).
A LOW on both pins initializes the FIFO read and write pointers to the first location of memory and
sets the Port B output register to all zeroes. A LOW-to-HIGH transition on
RS1
selects the programming
method (serial or parallel) and one of three programmable flag default offsets. It also configures Port
B for bus size and endian arrangement. Four LOW-to-HIGH transitions of CLKA and four LOW-to-
HIGH transitions of CLKB must occur while
RS1
is LOW.
A LOW on this pin initializes the FIFO read and write pointers to the first location of memory and sets
the Port B output register to all zeroes. During Partial Reset, the currently selected bus size, endian
arrangement, programming method (serial or parallel), and programmable flag settings are all retained.
A HIGH on this pin when BM is HIGH selects byte bus (9-bit) size on Port B. A LOW on this pin
when BM is HIGH selects word (18-bit) bus size. SIZE works with BM and BE to select the bus size
and endian arrangement for Port B. The level of SIZE must be static throughout device operation.
A LOW on this pin selects serial programming of partial flag offsets. A HIGH on this pin selects parallel
programming or default offsets (8, 16, or 64).
A HIGH selects a write operation and a LOW selects a read operation on Port A for a LOW-to-HIGH
transition of CLKA. The A0-A35 outputs are in the HIGH impedance state when W/RA is HIGH.
A LOW selects a write operation and a HIGH selects a read operation on Port B for a LOW-to-HIGH
transition of CLKB. The B0-B35 outputs are in the HIGH impedance state when
W/RB
is LOW.
MBF1
O
MBF2
Mail2 Register Flag
O
RS1, RS2
Resets
I
PRS
Partial Reset
I
SIZE
Bus Size Select
(Port B)
Serial Programming
Mode
Port A Write/
Read Select
Port B Write/
Read Select
I
SPM
W/RA
W/RB
I
I
I
5
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