SAA4955 Просмотр технического описания (PDF) - Philips Electronics
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SAA4955 Datasheet PDF : 28 Pages
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Philips Semiconductors
2.9-Mbit field memory
Product specification
SAA4955TJ
FEATURES
• 2949264-bit field memory
• 245772 × 12-bit organization
• 3.3 V power supply
• Inputs fully TTL compatible when using an extra 5 V
power supply
• High speed read and write operations
• FIFO operations:
– full word continuous read and write
– independent read and write pointers (asynchronous
read and write access)
– resettable read and write pointers
• Optional random access by block function (40 words per
block) enabled during pointer reset operation
• Quasi static (internal self-refresh and clocking pauses of
infinite length)
• Write mask function
• Cascade operation possible
• 16 Mbit CMOS DRAM process technology
• 40-pin SOJ Package.
GENERAL DESCRIPTION
The SAA4955TJ is a 2949264-bit field memory designed
for advanced TV applications such as 100/120 Hz TV,
PALplus, PIP and 3D comb filter. The maximum storage
depth is 245772 words × 12 bits. A FIFO operation with
full word continuous read and write could be used as a
data delay, for example. A FIFO operation with
asynchronous read and write could be used as a data rate
multiplier. Here the data is written once, then read as many
times as required without being overwritten by new data.
In addition to the FIFO operations, a random block access
mode is accessible during the pointer reset operation.
When this mode is enabled, reading and/or writing may
begin at, or proceed from, the start address of any of the
6144 blocks. Each block is 40 words in length. Two or
more SAA4955TJs can be cascaded to provide greater
storage depth or a longer delay, without the need for
additional circuitry.
The SAA4955TJ contains separate 12-bit wide serial ports
for reading and writing. The ports are controlled and
clocked separately, so asynchronous read and write
operations are supported. Independent read and write
clock rates are possible. Addressing is controlled by read
and write address pointers. Before a controlled write
operation can begin, the write pointer must be set to zero
or to the beginning of a valid address block. Likewise, the
read pointer must be set to zero or to the beginning of a
valid address block before a controlled read operation can
begin.
QUICK REFERENCE DATA
SYMBOL
PARAMETER
Tcy(SWCK)
Tcy(SRCK)
tACC
VDD, VDD(O)
VDD(P)
IDD(tot)
WRITE cycle time (SWCK)
READ cycle time (SRCK)
READ access time after SRCK
supply voltage (pins 19 and 22)
supply voltage (pins 20 and 21)
total supply current
(IDD(tot) = IDD + IDD(O) + IDD(P))
CONDITIONS
see Fig.3
see Fig.10
see Fig.10
minimum read/write cycle;
outputs open
MIN.
26
26
−
3.0
3.0
−
TYP.
−
−
−
3.3
3.3
22
MAX.
−
−
21
3.6
5.5
70
UNIT
ns
ns
ns
V
V
mA
ORDERING INFORMATION
TYPE
NUMBER
SAA4955TJ
NAME
SOJ40
PACKAGE
DESCRIPTION
plastic small outline package; 40 leads (J-bent); body width 10.16 mm
VERSION
SOT449-1
1999 Apr 29
2
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