3.3 VOLT CMOS SyncBiFIFO
TM
WITH BUS-MATCHING
256 x 36 x 2, 512 x 36 x 2,
1,024 x 36 x 2
FEATURES:
• Memory storage capacity:
IDT72V3624–256 x 36 x 2
IDT72V3634–512 x 36 x 2
IDT72V3644–1,024 x 36 x 2
• Clock frequencies up to 83 MHz (8ns access time)
• Two independent clocked FIFOs buffering data in opposite
directions
• Select IDT Standard timing (using
EFA EFB FFA
and
FFB
EFA, EFB, FFA,
flags functions) or First Word Fall Through Timing (using ORA,
ORB, IRA, and IRB 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
IDT72V3624
IDT72V3634
IDT72V3644
• Big- or Little-Endian format for word and byte bus sizes
• Master 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 coinci-
dent (simultaneous reading and writing of data on a single clock
edge is permitted)
• Auto power down minimizes power dissipation
• Available in space saving 128-pin Thin Quad Flatpack (TQFP)
• Pin and functionally compatible version of the 5V operating
IDT723624/723634/723644
• Industrial temperature range (–40
o
C to +85
o
C) is available
DESCRIPTION:
The IDT72V3624/72V3634/72V3644 are pin and functionally compatible
versions of the IDT723624/723634/723644, designed to run off a 3.3V supply
FUNCTIONAL BLOCK DIAGRAM
MBF1
Mail 1
Register
Output Bus-
Matching
Input
Register
Output
Register
CLKA
CSA
W/RA
ENA
MBA
MRS1
PRS1
Port-A
Control
Logic
36
RAM ARRAY
256 x 36
512 x 36
1,024 x 36
36
36
FIFO1,
Mail1
Reset
Logic
36
Write
Pointer
Read
Pointer
Status Flag
Logic
EFB/ORB
AEB
FFA/IRA
AFA
SPM
FS0/SD
FS1/SEN
A
0
-A
35
EFA/ORA
AEA
FIFO1
Programmable Flag
Offset Registers
9
FIFO2
Timing
Mode
FWFT
B
0
-B
35
Status Flag
Logic
Read
Pointer
Write
Pointer
36
FFB/IRB
AFB
36
Output
Register
Input Bus-
Matching
36
256 x 36
512 x 36
1,024 x 36
Mail 2
Register
36
Input
Register
RAM ARRAY
FIFO2,
Mail2
Reset
Logic
MRS2
PRS2
Port-B
Control
Logic
MBF2
CLKB
CSB
W/RB
ENB
MBB
BE
BM
SIZE
4664 drw 01
June 1999
1
©
1999
Integrated Device Technology, Inc.
DSC-4664/-
IDT72V3624/72V3634/72V3644
Commercial Temperature Range
DESCRIPTION (Continued)
for exceptionally low-power consumption. These devices are monolithic, high-
speed, low-power, CMOS bidirectional synchronous (clocked) FIFO memory
which supports clock frequencies up to 83 MHz and has read access times as
fast as 8ns. Two independent 256/512/1,024 x 36 dual-port SRAM FIFOs
on board each chip buffer data in opposite directions. FIFO data on Port B can
be input and output in 36-bit, 18-bit, or 9-bit formats with a choice of Big- or Little-
Endian configurations.
These devices are a synchronous (clocked) FIFO, 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
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.
PIN CONFIGURATION
CSA
FFA/IRA
EFA/ORA
PRS1
Vcc
AFA
AEA
MBF2
MBA
MRS1
FS0/SD
GND
GND
FS1/SEN
MRS2
MBB
MBF1
Vcc
AEB
AFB
EFB/ORB
FFB/IRB
GND
CSB
W/RB
ENB
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
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
CLKB
PRS2
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
4664 drw 02
TQFP (PK128-1, order code: PF)
TOP VIEW
2
IDT72V3624/72V3634/72V3644
Commercial Temperature Range
Communication between each port may bypass the FIFOs 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: Master Reset and Partial
Reset. Master Reset initializes the read and write pointers to the first location of
the memory array, configures the FIFO for Big- or Little-Endian byte arrange-
ment and selects serial flag programming, parallel flag programming, or one of
three possible default flag offset settings, 8, 16 or 64. There are two Master Reset
pins,
MRS1
and
MRS2.
Partial Reset also sets the read and write pointers to the first location of the
memory. Unlike Master 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. Each FIFO has its own, independent Partial Reset pin,
PRS1
and
PRS2.
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 long-
word (36-bit wide) written to an empty FIFO appears automatically on the
outputs, no read operation is required (Nevertheless, accessing subsequent
words does necessitate a formal read request). The state of the BE/FWFT pin
during FIFO operation determines the mode in use.
Each FIFO has a combined Empty/Output Ready Flag (EFA/ORA and
EFB/ORB)
and a combined Full/Input Ready Flag (FFA/IRA and
FFB/IRB).
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 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.
Each FIFO has a programmable Almost-Empty flag (AEA and
AEB)
and a programmable Almost-Full flag (AFA and
AFB). AEA
and
AEB
indicate when a selected number of words remain in the FIFO memory.
AFA
and
AFB
indicate when the FIFO contains more than a selected number of
words.
FFA/IRA, FFB/IRB, AFA
and
AFB
are two-stage synchronized to the
port clock that writes data into its array.
EFA/ORA, EFB/ORB, AEA
and
AEB
are two-stage synchronized to the port clock that reads data from its array.
Programmable offsets for
AEA, AEB, AFA
and
AFB
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
AEA
and
AEB
threshold can be set at 8, 16 or 64 locations from the empty
boundary and the
AFA
and
AFB
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 Master Reset.
Two or more devices may be used in parallel to create wider data paths.
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 IDT72V3624/72V3634/72V3644 are characterized for operation from
o
0 C to 70
o
C. Industrial temperature range (-40
o
C to +85
o
C) is available. They
are fabricated using IDT’s high speed, submicron CMOS technology.
3
IDT72V3624/72V3634/72V3644
Commercial Temperature Range
PIN DESCRIPTIONS
Symbol
A0-A35
AEA
AEB
AFA
AFB
B0-B35
BE/FWFT
Name
Port A Data
Port A Almost-
Empty Flag
Port B Almost-
Empty Flag
Port A Almost-
Full Flag
Port B Almost-
Full Flag
Port A Data
Big-Endian/
First Word
Fall Through
Select
I/O
I/O
O
O
O
O
I/O
I
36-bit bidirectional data port for side A.
Programmable Almost-Empty flag synchronized to CLKA. It is LOW when the number of words in
FIFO2 is less than or equal to the value in the Almost-Empty A Offset register, X2.
Programmable Almost-Empty flag synchronized to CLKB. It is LOW when the number of words in
FIFO1 is less than or equal to the value in the Almost-Empty B Offset register, X1.
Programmable Almost-Full flag synchronized to CLKA. It is LOW when the number of empty
locations in FIFO1 is less than or equal to the value in the Almost-Full A Offset register, Y1.
Programmable Almost-Full flag synchronized to CLKB. It is LOW when the number of empty
locations in FIFO2 is less than or equal to the value in the Almost-Full B Offset register, Y2.
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 on Port A is read from
Port B first (A-to-B data flow) or written to Port B first (B-to-A data flow). A LOW on BE will select
Little-Endian operation. In this case, the least significant byte or word on Port A is read from Port B
first (for A-to-B data flow) or written to Port B first (B-to-A data flow). 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.
FFA/IRA, EFA/ORA, AFA,
and
AEA
are all 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.
FFB/IRB, EFB/ORB, AFB,
and
AEB
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
EFA
function is selected.
EFA
indicates whether or not the FIFO2 memory is empty. In the FWFT mode, the ORA function is
selected. ORA indicates the presence of valid data on A0-A35 outputs, available for reading.
EFA/ORA
is synchronized to the LOW-to-HIGH transition of CLKA.
This is a dual function pin. In the IDT Standard mode, the
EFB
function is selected.
EFB
indicates
whether or not the FIFO1 memory is empty. In the FWFT mode, the ORB function is selected. ORB
indicates the presence of valid data on the B0-B35 outputs, available for reading.
EFB/ORB
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
FFA
function is selected.
FFA
indicates
whether or not the FIFO1 memory is full. In the FWFT mode, the IRA function is selected. IRA
indicates whether or not there is space available for writing to the FIFO1 memory.
FFA/IRA
is
synchronized to the LOW-to-HIGH transition of CLKA.
This is a dual function pin. In the IDT Standard mode, the
FFB
function is selected.
FFB
indicates
whether or not the FIFO2 memory is full. In the FWFT mode, the IRB function is selected. IRB
indicates whether or not there is space available for writing to the FIFO2 memory.
FFB/IRB
is
synchronized to the LOW-to-HIGH transition of CLKB.
4
Description
BM
Bus-Match Select
(Port B)
Port A Clock
I
CLKA
I
CLKB
Port B Clock
I
CSA
CSB
EFA/ORA
Port A Chip Select
Port B Chip Select
Port A Empty/
Output Ready Flag
I
I
O
EFB/ORB
Port B Empty/
Output Ready Flag
O
ENA
ENB
FFA/IRA
Port A Enable
Port B Enable
Port A Full/
Input Ready Flag
I
I
O
FFB/IRB
Port B Full/
Input Ready Flag
O
IDT72V3624/72V3634/72V3644
Commercial Temperature Range
PIN DESCRIPTIONS (Continued)
Symbol
FS1/SEN
Name
Flag Offset Select 1/
Serial Enable,
FS0/SD
Flag Offset Select 0/
Serial Data
I/O
I
Description
FS1/SEN and FS0/SD are dual-purpose inputs used for flag offset register programming. During
Master 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 32 for the 72V3624, 36 for the 72V3634, and 40 for the 72V3644.
The first bit write stores the Y-register (Y1) MSB and the last bit write stores the X-register (X2) LSB.
A HIGH level on MBA chooses a mailbox register for a Port A read or write operation. When
the A0-A35 outputs are active, a HIGH level on MBA selects data from the mail2 register for output
and a LOW level selects FIFO2 output register data for output.
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 FIFO1 output register 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 Master or Partial Reset of FIFO1.
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 Master or Partial Reset of FIFO2.
A LOW on this pin initializes the FIFO1 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
MRS1
selects the programming
method (serial or parallel) and one of three programmable flag default offsets for FIFO1 and FIFO2. 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
MRS1
is LOW.
A LOW on this pin initializes the FIFO2 read and write pointers to the first location of memory and sets
the Port A output register to all zeroes. A LOW-to-HIGH transition on
MRS2,
toggled simultaneously
with
MRS1,
selects the programming method (serial or parallel) and one of the programmable flag default
offsets for FIFO2. Four LOW-to-HIGH transitions of CLKA and four LOW-to-HIGH transitions of CLKB
must occur while
MRS2
is LOW.
A LOW on this pin initializes the FIFO1 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 LOW on this pin initializes the FIFO2 read and write pointers to the first location of memory and sets
the Port A 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.
I
MBA
Port A Mailbox
Select
Port B Mailbox
Select
Mail1 Register
Flag
I
MBB
I
MBF1
O
MBF2
Mail2 Register
Flag
O
MRS1
FIFO1 Master
Reset
I
MRS2
FIFO2 Master
Reset
I
PRS1
FIFO1 Partial
Reset
FIFO2 Partial
Reset
Bus Size Select
I
PRS2
I
SIZE
I
SPM
W/RA
W/RB
Serial
Programming Mode
Port-A Write/
Read Select
Port-B Write/
Read Select
I
I
I
5
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