BiCMOS Static RAM
240K (16K x 15-Bit)
Cache-Tag RAM
IDT71215
for the Pentium™ Processor
stored TAG bits and the current Tag input data. An active HIGH
MATCH output is generated when these two groups of data are the
same for a given address. This high-speed MATCH signal, with tADM
as fast as 8ns, provides the fastest possible enabling of secondary
cache accesses.
Features
◆
16K x 15 Configuration
– 12 TAG Bits
– 3 Separate I/O Status Bits (Valid, Dirty, Write Through)
Match output uses Valid bit to qualify MATCH output
High-Speed Address-to-Match comparison times
◆
The three separate I/O status bits (VLD, DTY, and WT) can be
configured for either dedicated or generic functionality, depending on
the SFUNC input pin. With SFUNC LOW, the status bits are defined
and used internally by the device, allowing easier determination of the
validity and use of the given Tag data. SFUNC HIGH releases the
defined internal status bit usage and control, allowing the user to
configure the status bit information to fit his system needs. A synchro-
nous RESET pin, when held LOW at a rising clock edge, will reset all
status bits in the array for easy invalidation of all Tag addresses.
The IDT71215 also provides the option for Burst Ready (BRDY)
generation within the cache tag itself, based upon MATCH, VLD bit,
WT bit, and external inputs provided by the user. This can significantly
simplify cache controller logic and minimize cache decision time.
Match and Read operations are both asynchronous in order to
provide the fastest access times possible, while Write operations are
synchronous for ease of system timing.
The IDT71215 uses a 5V power supply on VCC with separate VCCQ
pins provided for the outputs to offer compliance with both 5V TTL and
3.3V LVTTL Logic levels. The PWRDN pin offers a low-power standby
mode to reduce power consumption by 90%, providing significant
system power savings.
The IDT71215 is fabricated using IDT’s high-performance, high-
reliability BiCMOS technology and is offered in a space-saving 80-pin
Thin Plastic Quad Flat Pack (TQFP) package.
◆
– 8/9/10/12ns over commercial temperature range
BRDY circuitry included inside the Cache-Tag for
highest speed operation
◆
◆
Asynchronous Read/Match operation with Synchronous
Write and Reset operation
◆
Separate WE for the TAG bits and the Status bits
◆
Separate OE for the TAG bits, the Status bits, and BRDY
◆
Synchronous RESET pin for invalidation of all Tag
entries
◆
Dual Chip selects for easy depth expansion with no
performance degredation
I/O pins both 5V TTL and 3.3V LVTTL compatible with
◆
VCCQ pins
◆
PWRDN pin to place device in low-power mode
Packaged in a 80-pin Thin Plastic Quad Flat Pack (TQFP).
◆
Description
The IDT71215 is a 245,760-bit Cache Tag Static RAM, orga-
nized 16K x 15 and designed to support the Pentium and other Intel
processors at bus speeds up to 66MHz. There are twelve common
I/O TAG bits, with the remaining three bits used as status bits. A 12-
bit comparator is on-chip to allow fast comparison of the twelve
Pin Descriptions
0
13
A – A
Address Inputs
Input
Input
Input
Input
Input
Input
Input
Input
Input
CLK
System Clock
Input
Input
Input
Input
Output
I/O
Chip Selects
BRDYH
CS1, CS2
WET
BRDY Force High
BRDY Output Enable
Additional BRDY Input
Burst Ready
Write Enable – Tag Bits
Write Enable – Status Bits
Output Enable – Tag Bits
Output Enable – Status Bits
Status Bit Reset
BRDYOE
BRDYIN
BRDY
0
WES
OET
11
TAG – TAG
Tag Data Input/Outputs
OES
OUT 1OUT
VLD /S
1
Valid Bit/S Bit Output
Output
Output
RESET
PWRDN
SFUNC
W/R
OUT 2OUT
DTY /S
2
Powerdown Mode Control Pin
Status Bit Function Control Pin
Dirty Bit/S Bit Output
OUT 3OUT
WT /S
3
Write Through Bit/S Bit Output Output
Write/Read Input from Processor Input
MATCH
Match
Output
Pwr
IN 1IN
1
CC
V
VLD /S
Valid Bit/S Bit Input
Input
Input
Input
+5V Power
Output Buffer Power
Ground
IN 2IN
2
CCQ
V
DTY /S
Dirty Bit/S Bit Input
QPwr
Gnd
IN 3IN
3
SS
V
WT /S
Write Through Bit/S Bit Input
3075 tbl 01
Pentium is a trademark of Intel Corporation.
OCTOBER 1999
1
©1999 Integrated Device Technology, Inc.
DSC-3075/04