AUSTIN MT42C4256C

VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
256K X 4 VRAM
PIN ASSIGNMENT
(Top View)
256K x 4 DRAM
with 512K x 4 SAM
28-Pin DIP (C)
(400 MIL)
AVAILABLE AS MILITARY
SPECIFICATIONS
SC
SDQ1
SDQ2
TR\/OE\
DQ1
DQ2
ME\/WE\
NC
RAS\
A8
A6
A5
A4
Vcc
• SMD 5962-89497
• MIL-STD-883
FEATURES
• Class B High-Reliability Processing
• DRAM: 262144 Words × 4 Bits
SAM: 512 Words × 4 Bits
• Single 5-V Power Supply (±10% Tolerance)
• Dual Port Accessibility–Simultaneous and Asynchronous Access
From the DRAM and SAM Ports
• Bidirectional-Data-Transfer Function Between the DRAM and the
Serial-Data Register
• 4 × 4 Block-Write Feature for Fast Area Fill Operations; As Many
as Four Memory Address Locations Written per Cycle From an
On-Chip Color Register
• Write-Per-Bit Feature for Selective Write to Each RAM I/O; Two
Write-Per-Bit Modes to Simplify System Design
• Enhanced Page-Mode Operation for Faster Access
• CAS-Before-RAS (CBR) and Hidden Refresh Modes
• All Inputs/Outputs and Clocks Are TTL Compatible
• Long Refresh Period: Every 8 ms (Max)
• Up to 33-MHz Uninterrupted Serial-Data Streams
• 3-State Serial I/Os Allow Easy Multiplexing of Video-Data
Streams
• 512 Selectable Serial-Register Starting
• Split Serial-Data Register for Simplified Real-Time Register Reload
OPTIONS
• Timing
100ns, 30ns/27ns
120ns, 35ns/35ns
• Package(s)
Ceramic SOJ
Ceramic DIP (400 mil)
Ceramic LCC
Ceramic Flat Pack
Ceramic ZIP
Ceramic LCC
Vss
SDQ4
SDQ3
SE\
DQ4
DQ3
DSF
CAS\
QSF
A0
A1
A2
A3
A7
SC
SDQ1
SDQ2
TR\/OE\
DQ1
DQ2
ME\/WE\
NC
RAS\
A8
A6
A5
A4
Vcc
DSF
DQ3
SDQ2
Vss
SDQ0
TRG\
DQ1
GND
A8
A5
Vcc
A3
A1
QSF
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Vss
SDQ4
SDQ3
SE\
DQ4
DQ3
DSF
CAS\
QSF
A0
A1
A2
A3
A7
1
3
5
7
9
11
13
15
17
19
21
23
25
27
2
4
6
8
10
12
14
16
18
20
22
24
26
28
DQ2
SE\
SDQ3
SC
SDQ1
DQ0
W\
RAS\
A8
A4
A7
A2
A0
CAS\
28-Pin FP (F)
SC
SDQ1
SDQ2
TR\/OE\
DQ1
DQ2
ME\/WE\
NC
RAS\
A8
A6
A5
A4
Vcc
-10
-12
SMJ Prefix
--JDM
HMM
--SVM
HJM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
PIN NAME
PIN NAME
(SMJ)
(MT)
A0 - A8
A0 - A8
CAS\
CAS\
DQ0 - DQ3
DQ1 - DQ4
SE\
SE\
RAS\
RAS\
SC
SC
SDQ0 - SDQ3 SDQ1 - SDQ4
TRG\
TR\ /OE\
W\
ME\ /WE\
DSF
DSF
QSF
QSF
Vcc
Vcc
Vss
Vss
For more products and information
please visit our web site at
www.austinsemiconductor.com
GND
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
28
27
26
25
24
23
22
21
20
19
18
17
16
15
28-Pin ZIP (CZ)
MARKING
MT Prefix
DCJ
C
EC
F
CZ
---
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28-Pin SOJ (DCJ)
28-Pin LCC (EC)
NC
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Vss
SDQ4
SDQ3
SE\
DQ4
DQ3
DSF
CAS\
QSF
A0
A1
A2
A3
A7
DESCRIPTION
Address Inputs
Column Enable
DRAM Data In-Out/Write-Mask Bit
Serial Enable
Row Enable
Serial Data Clock
Serial Data In-Out
Transfer Register/Q Output Enable
Write-Mask Select/Write Enable
Special Function Select
Split-Register Activity Status
5V Supply
Ground
Ground (Important: Not Connected to
internal Vss, Pin should be left open or
tied to ground.
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
1
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
DESCRIPTION
half and a low half. While one half is being read out of the SAM
port, the other half can be loaded from the memory array. For
applications not requiring real-time register reload (for example,
reloads done during CRT retrace periods), the single-register
mode of operation is retained to simplify design. The SAM can
also be configured in input mode, accepting serial data from an
external device. Once the serial register within the SAM is
loaded, its contents can be transferred to the corresponding
column positions in any row in memory in a single memory
cycle.
The SAM port is designed for maximum performance. Data
can be input to or accessed from the SAM at serial rates up to
33 MHz. During the split-register mode of operation, internal
circuitry detects when the last bit position is accessed from the
active half of the register and immediately transfers control to
the opposite half. A separate output, QSF, is included to
indicate which half of the serial register is active at any given
time in the split-register mode.
All inputs, outputs, and clock signals on the SMJ44C251B/
MT42C4256 are compatible with Series 54 TTL devices. All address lines and data-in lines are latched on-chip to simplify
system design. All data-out lines are unlatched to allow greater
system flexibility.
Enhanced page-mode operation allows faster memory
access by keeping the same row address while selecting
random column addresses. The time for row-address setup,
row-address hold, and address multiplex is eliminated, and a
memory cycle time reduction of up to 3× can be achieved,
compared to minimum RAS cycle times. The maximum number
of columns that can be accessed is determined by the maximum
RAS low time and page-mode cycle time used. The
SMJ44C251B/MT42C4256 allows a full page (512 cycles) of
information to be accessed in read, write, or read-modify-write
mode during a single RAS-low period using relatively conservative page-mode cycle times.
The SMJ44C251B/MT42C4256 employs state-of-the-art
technology for very high performance combined with improved
reliability.
The SMJ44C251B/MT42C4256 multiport video RAM is a
high-speed, dual-ported memory device. It consists of a
dynamic random-access memory (DRAM) organized as 262144
words of 4 bits each interfaced to a serial-data register or serialaccess memory (SAM) organized as 512 words of 4 bits each.
The SMJ44C251B/MT42C4256 supports three types of
operation: random access to and from the DRAM, serial access
to and from the serial register, and bidirectional transfer of data
between any row in the DRAM and the serial register. Except
during transfer operations, the SMJ44C251B/MT42C4256 can
be accessed simultaneously and asynchronously from the
DRAM and SAM ports.
During a transfer operation, the 512 columns of the DRAM
are connected to the 512 positions in the serial data register.
The 512 × 4-bit serial-data register can be loaded from the
memory row (transfer read), or the contents of the 512 × 4-bit
serial-data register can be written to the memory row (transfer
write).
The SMJ44C251B/MT42C4256 is equipped with several
features designed to provide higher system-level bandwidth
and to simplify design integration on both the DRAM and SAM
ports. On the DRAM port, greater pixel draw rates can be
achieved by the device’s 4 × 4 block-write mode. The blockwrite mode allows four bits of data (present in an on-chip colordata register) to be written to any combination of four adjacent
column-address locations. As many as 16 bits of data can be
written to memory during each CAS cycle time. Also on the
DRAM port, a write mask or a write-per-bit feature allows masking any combination of the four input/outputs on any write
cycle. The persistent write-per-bit feature uses a mask register
that, once loaded, can be used on subsequent write cycles. The
mask register eliminates having to provide mask data on every
mask-write cycle.
The SMJ44C251B/MT42C4256 offers a split-register
transfer read (DRAM to SAM) feature for the serial tester (SAM
port). This feature enables real-time register reload
implementation for truly continuous serial data streams without
critical timing requirements. The register is divided into a high
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
2
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FUNCTIONAL BLOCK DIAGRAM
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
3
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
FUNCTION TABLE
CAS\
FALL
RAS\ FALL
FUNCTION
1
CAS\
TRG\
W\
DSF
SE\
DSF
L
X
X
X
X
X
H
L
L
X
L
X
H
L
L
H
X
X
H
L
L
L
H
X
H
L
H
L
X
X
H
L
H
H
X
X
H
L
L
L
X
L
H
H
L
L
X
H
H
H
L
H
X
L
H
H
L
H
X
H
H
H
H
L
X
L
H
H
H
L
X
H
Load write mask
H
H
H
H
X
L
Load color register
H
H
H
H
X
H
CBR Refresh
Register-to-memory transfer
(transfer write)
Alternate transfer write
(independent of SE\)
Serial-write-mode enable
(pseudo-transfer write)
Memory-to-register transfer
(transfer read)
Split-register-transfer read
(must reload tap)
Load and use write mask,
Write data to DRAM
Load and use write mask,
Block write to DRAM
Persistent write-per-bit,
Write data to DRAM
Persistent write-per-bit,
Block write to DRAM
Normal DRAM read/write
(nonmasked)
Block write to DRAM
(nonmasked)
ADDRESS
RAS\
CAS\
X
X
Row
Tap
Addr
Point
Row
Tap
Addr
Point
Refresh
Tap
Addr
Point
Row
Tap
Addr
Point
Row
Tap
Addr
Point
Row
Col
Addr
Addr
Row Blk Addr
Addr
A2-A8
Row
Col
Addr
Addr
Row Blk Addr
A2-A8
Addr
Row
Col
Addr
Addr
Row Blk Addr
A2-A8
Addr
Refresh
X
Addr
Refresh
X
Addr
DQ0 - DQ3
RAS\ CAS\
W\
X
X
2
3
TYPE
R
X
X
T
X
X
T
X
X
T
X
X
T
X
X
T
DQ
Mask
DQ
Mask
Valid
Data
Col
Mask
Valid
Data
Col
Mask
Valid
Data
Col
Mask
DQ
Mask
Color
Data
X
X
X
X
X
X
R
R
R
R
R
R
R
R
NOTES:
1. In persistent write-per-bit function, W\ must be high during the refresh cycle.
2. DQ0 - DQ3 are latched on the later of W\ or CAS\ falling edge. Col Mask = H: Write to address/column location enabled.
DQ Mask = H: Write to I/O enabled.
3. R = random access operation, T = transfer operation.
LEGEND
H = HIGH
L = LOW
X = Don’t Care
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
4
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
DETAILED SIGNAL DESCRIPTION VS. OPERATIONAL MODE
PIN
A0 - A8
CAS\
DQi
DSF
RAS\
SE\
SC
SDQ
TRG\
W\
DRAM
Row, column address
Column enable, output enable
DRAM data I/O, write mask bits
Block-write enable
Persistent write-per-bit enable
Color-register load enable
Row enable
Q output enable
Write enable, write-per-bit select
TRANSFER
Row, tap address
Tap-address strobe
Split-register enable
Alternative write-transfer enable
Row enable
Serial-in mode enable
Vcc
Vss
Serial enable
Serial clock
Serial-data I/O
Transfer enable
Transfer-write enable
Split register
Active status
QSF
NC/GND
SAM
Make no external connection or tie
to system Vss
5V supply (typical)
Device ground
ROW-ADDRESS STROBE (RAS\)
RAS\ is similar to a chip enable because all DRAM cycles
and transfer cycles are initiated by the falling edge of RAS\.
RAS\ is a control input that latches the states of row address,
W\, TRG\, SE\, CAS\, and DSF onto the chip to invoke DRAM
and transfer functions.
OPERATION
Depending on the type of operation chosen, the signals of
the SMJ44C251B/MT42C4256 perform different functions. The
“Detailed Signal Description vs. Operational Mode” table
summarizes the signal descriptions and the operational modes
they control.
The SMJ44C251B/MT42C4256 has three kinds of
operations: random-access operations typical of a DRAM,
transfer operations from memory arrays to the SAM, and serialaccess operations through the SAM port. The signals used to
control these operations are described here, followed by
discussions of the operations themselves.
COLUMN-ADDRESS STROBE (CAS\)
CAS\ is a control input that latches the states of column
address and DSF to control DRAM and transfer functions.
When CAS\ is brought low during a transfer cycle, it latches
the new tap point for the serial-data input or output. CAS\ also
acts as an output enable for the DRAM outputs DQ0–DQ3.
ADDRESS (A0–A8)
For DRAM operation, 18 address bits are required to
decode one of the 262144 storage cell locations. Nine rowaddress bits are set up on A0–A8 and latched onto the chip on
the falling edge of RAS\. Nine column-address bits are set up
on A0–A8 and latched onto the chip on the falling edge of
CAS\. All addresses must be stable on or before the falling
edges of RAS\ and CAS\.
During the transfer operation, the states of A0–A8 are
latched on the falling edge of RAS\ to select one of the 512
rows where the transfer occurs. To select one of 512 tap points
(starting positions) for the serial-data input or output, the
appropriate 9-bit column address (A0–A8) must be valid when
CAS\ falls.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
OUTPUT ENABLE/TRANSFER SELECT (TRG\)
TRG\ selects either DRAM or transfer operation as RAS\
falls. For DRAM operation, TRG\ must be held high as RAS\
falls. During DRAM operation, TRG\ functions as an output
enable for the DRAM outputs DQ0–DQ3. For transfer
operation, TRG\ must be brought low before RAS\ falls.
WRITE-MASK SELECT, WRITE ENABLE (W\)
In DRAM operation, W\ enables data to be written to the
DRAM. W\ is also used to select the DRAM write-per-bit mode.
Holding W\ low on the falling edge of RAS\ invokes the writeper-bit operation. The SMJ44C251B/MT42C4256 supports both
the normal write-per-bit mode and the persistent write-per-bit
mode.
CONTINUED
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
5
VRAM
Austin Semiconductor, Inc.
WRITE-MASK SELECT, WRITE ENABLE (W\)
(continued)
For transfer operation, W\ selects either a read-transfer
operation (DRAM to SAM) or a write-transfer operation (SAM
to DRAM). During a transfer cycle, if W is high when RAS\
falls, a read transfer occurs; if W is low, a write transfer occurs.
serial-output mode, data in SAM is accessed from the least
significant bit to the most significant bit. The data registers
operate modulo 512; so after bit 511 is accessed, the next bits to
be accessed are 00, 01, 02, etc. If the previous transfer cycle was
either a write transfer or a pseudo transfer, the data register is in
serial-input mode and signal data can be input to the register.
SPECIAL FUNCTION SELECT (DSF)
DSF is latched on the falling edge of RAS\ or CAS\, similar
to an address. DSF determines which of the following functions
are invoked on a particular cycle:
• Persistent write-per-bit
• Block write
• Split-register transfer read
• Mask-register load for the persistent write-per-bit mode
• Color-register load for the block-write mode
SERIAL CLOCK (SC)
Serial data is accessed in or out of the data register on the
rising edge of SC. The SMJ44C251B/MT42C4256 is designed
to work with a wide range of clock-duty cycles to simplify
system design. There is no refresh requirement because the
data registers that comprise the SAM are static. There is also
no minimum SC clock operating frequency.
SERIAL ENABLE (SE\)
During serial-access operations SE\ is used as an enable/
disable for SDQ in both the input and output modes. If SE\ is
held as RAS\ falls during a write-transfer cycle, a pseudotransfer write occurs. There is no actual transfer, but the data
register switches from the output mode to the input mode.
DRAM DATA I/O, WRITE-MASK DATA (DQ0–DQ3)
DRAM data is written via DQ terminals during a write or
read-modify-write cycle. In an early-write cycle, W\ is brought
low prior to CAS\ and the data is strobed in by CAS\ with data
setup and hold times referenced to this signal. In a delayedwrite or read-modify-write cycle, W\ is brought low after CAS\
and the data is strobed in by W\ with data setup and hold times
referenced to this signal.
The 3-state DQ output buffers provide direct TTL
compatibility (no pullup resistors) with a fanout of two Series 54
TTL loads. Data out is the same polarity as data in. The outputs
are in the high-impedance (floating) state as long as CAS\ and
TRG\ are held high. Data does not appear at the outputs until
both CAS\ and TRG\ are brought low. Once the outputs are
valid, they remain valid while CAS\ and TRG\ are low. CAS\ or
TRG\ going high returns the outputs to the high-impedance
state. In a register-transfer operation, the DQ outputs remain in
the high-impedance state for the entire cycle.
The write-per-bit mask is latched into the device via the
random DQ terminals by the falling edge of RAS\. This mask
selects which of the four random I/Os are written.
NO CONNECT/GROUND (NC/GND)
NC/GND is reserved for the manufacturer’s test operation.
It is an input and should be tied to system ground or left
floating for proper device operation.
SPECIAL FUNCTION OUTPUT (QSF)
During split-register operation the QSF output indicates
which half of the SAM is being accessed. When QSF is low, the
serial-address pointer is accessing the lower (least significant)
256 bits of SAM. When QSF is high, the serial-address pointer
is accessing the higher (most significant) 256 bits of SAM. QSF
changes state upon crossing the boundary between the two
SAM halves in the split-register mode.
During normal transfer operations QSF changes state upon
completing a transfer cycle. This state is determined
by the tap point being loaded during the transfer cycle.
POWER UP
To achieve proper device operation, an initial pause of
200ms is required after power-up, followed by a minimum of
eight RAS\ cycles or eight CBR cycles, a memory-to-register
transfer cycle, and two SC cycles.
SERIAL DATA I/O (SDQ0–SDQ3)
Serial inputs and serial outputs share common I/O
terminals. Serial-input or serial-output mode is determined by
the previous transfer cycle. If the previous transfer cycle was a
read transfer, the data register is in serial-output mode. While in
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
6
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
RANDOM-ACCESS-OPERATION FUNCTIONS
CAS\
FALL
RAS\ FALL
FUNCTION
DQ0 - DQ3
2
1
CAS\
TRG\
W\
DSF
SE\
DSF
L
X
X
X
X
X
H
H
L
L
X
L
H
H
L
L
X
H
H
H
L
H
X
L
H
H
L
H
X
H
H
H
H
L
X
L
H
H
H
L
X
H
Load write mask
H
H
H
H
X
L
Load color register
H
H
H
H
X
H
CBR Refresh
Load and use write mask,
Write data to DRAM
Load and use write mask,
Block write to DRAM
Persistent write-per-bit,
Write data to DRAM
Persistent write-per-bit,
Block write to DRAM
Normal DRAM read/write
(nonmasked)
Block write to DRAM
(nonmasked)
ADDRESS
RAS\
CAS\
X
X
Row
Col
Addr
Addr
Row Blk Addr
Addr
A2-A8
Row
Col
Addr
Addr
Row Blk Addr
Addr
A2-A8
Row
Col
Addr
Addr
Row Blk Addr
Addr
A2-A8
Refresh
X
Addr
Refresh
X
Addr
RAS\ CAS\
W\
X
X
DQ
Valid
Mask Data
DQ
Col
Mask Mask
Valid
X
Data
Col
X
Mask
Valid
X
Data
Col
X
Mask
DQ
X
Mask
Color
X
Data
NOTES:
1. In persistent write-per-bit function, W must be high during the refresh cycle.
2. DQ0–DQ3 are latched on the later of W or CAS falling edge. Col Mask = H: Write to address/column location enabled.
DQ Mask = H: Write to I/O enabled
LEGEND:
H = High
L = Low
X = Don’t care
RANDOM-ACCESS OPERATION
The random-access operation functions are summarized in
the “Random-Access-Operation Function” table and described
in the following sections.
row-address hold time has been satisfied, usually well in advance of the falling edge of CAS\. In this case, data can be
obtained after ta(C) max (access time from CAS low), if ta(CA) max
(access time from column address) has been satisfied.
ENHANCED PAGE-MODE
REFRESH
Enhanced page-mode operation allows faster memory
access by keeping the same row address while selecting
random column addresses. This mode eliminates the time
required for row address setup-and-hold and address
multiplex. The maximum RAS\ low time and the CAS\ page cycle
time used determine the number of columns that can be
accessed.
Unlike conventional page-mode operation, the enhanced
page mode allows the SMJ44C251B/MT42C4256 to operate at a
higher data bandwidth. Data retrieval begins as soon as the
column address is valid rather than when CAS\ transitions low.
A valid column address can be presented immediately after
There are three types of refresh available on the
SMJ44C251B/MT42C4256: RAS\-only refresh, CBR refresh, and
hidden refresh.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
RAS\-ONLY REFRESH
A refresh operation must be performed to each row at least
once every 8 ms to retain data. Unless CAS\ is applied, the
output buffers are in the high-impedance state, so the RAS\only refresh sequence avoids any output during refresh. Externally generated addresses must be supplied during RAS-only
refresh. Strobing each of the 512 row addresses with RAS causes
(continued)
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
7
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
RAS\-ONLY REFRESH (continued)
BLOCK WRITE
all bits in each row to be refreshed. CAS\ can remain high
(inactive) for this refresh sequence to conserve power.
The block-write mode allows data (present in an on-chip
color register) to be written into four consecutive
column-address locations. The 4-bit color register is loaded by
the color-register-load cycle. Both write-per-bit modes can be
applied in the block-write cycle. The block-write mode also
offers the 4 × 4 column-mask capability.
CAS\-BEFORE-RAS\ (CBR) REFRESH
CBR refresh is accomplished by bringing CAS\ low earlier
than RAS\. The external row address is ignored and the refresh
row address is generated internally when using CBR refresh.
Other cycles can be performed in between CBR cycles without
disturbing the internal address generation.
LOAD COLOR REGISTER
The load-color-register cycle is performed using normal
DRAM write-cycle timing except that DSF is held high on the
falling edges of RAS\ and CAS\. A 4-bit code is input to the
color register via the random I/O terminals and latched on the
later of the falling edge of CAS\ or W\. After the color register is
loaded, it retains data until power is lost or until another loadcolor-register cycle is executed.
HIDDEN REFRESH
A hidden refresh is accomplished by holding CAS\ low in
the DRAM-read cycle and cycling RAS\. The output data of
the DRAM-read cycle remains valid while the refresh is being
carried out. Like the CBR refresh, the refreshed row addresses
are generated internally during the hidden refresh.
BLOCK WRITE CYCLE
WRITE-PER-BIT
After the color register is loaded, the block-write cycle can
begin as a normal DRAM write cycle with DSF held high on the
falling edge of CAS\ (see Figures 2, 3, and 4). When the blockwrite cycle is invoked, each data bit in the 4-bit color register is
written to selected bits of the four adjacent columns of the
corresponding random I/O.
During block-write cycles, only the seven most significant
column addresses (A2–A8) are latched on the falling edge of
CAS\. The two least significant addresses (A0–A1) are replaced
by four DQ bits (DQ0–DQ3), which are also latched on the later
of the falling edge of CAS\ or W\. These four bits are used as a
column mask, and they indicate which of the four
column-address locations addressed by A2–A8 are written with
the contents of the color register during the block-write cycle.
DQ0 enables a write to column-address A1 = 0 (low), A0 = 0
(low); DQ1 enables a write to column-address A1 = 0 (low),
A0 = 1 (high); DQ2 enables a write to column-address A1 = 1
(high), A0 = 0 (low); DQ3 enables a write to column-address A1
= 1 (high), A0 = 1 (high). A high logic level enables a write, and
a low logic level disables the write. A maximum of 16 bits (4 × 4)
can be written to memory during each CAS\ cycle in the blockwrite mode.
The write-per-bit feature allows masking of any
combination of the four DQs on any write cycle (see Figure 1).
The write-per-bit operation is invoked only when W\ is held
low on the falling edge of RAS\. If W\ is held high on the falling
edge of RAS\, write-per-bit is not enabled and the write
operation is performed to all four DQs. The SMJ44C251B/
MT42C4256 offers two write-per-bit modes: the nonpersistent
write-per-bit mode and the persistent write-per-bit mode.
NONPERSISTENT WRITE-PER-BIT
When DSF is low on the falling edge of RAS\, the write
mask is reloaded. A 4-bit code (the write-per-bit mask) is input
to the device via the random DQ terminals and latched on the
falling edge of RAS\. The write-per-bit mask selects which of
the four random I/Os are written and which are not. After RAS\
has latched the on-chip write-per-bit mask, input data is driven
onto the DQ terminals and is latched on the later falling edge of
CAS\ or W\. When a data low is strobed into a particular I/O on
the falling edge of RAS\, data is not written to that I/O. When
a data high is strobed into a particular I/O on the falling edge of
RAS\, data is written to that I/O.
PERSISTENT WRITE-PER-BIT
When DSF is high on the falling edge of RAS\, the writeper-bit mask is not reloaded: it retains the value stored during
the last write-per-bit mask reload. This mode of operation is
known as persistent write-per-bit because the write-per-bit mask
is persistent over an arbitrary number of write cycles. The writeper-bit mask reload can be done during the nonpersistent writeper-bit cycle or by the mask-register-load cycle.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
8
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 1: EXAMPLE OF WRITE-PER-BIT OPERATIONS
DQ Mask = H: Write to I/O enable
= L: Write to I/O disable
FIGURE 2: EXAMPLE BLOCK-WRITE DIAGRAM OPERATIONS
NOTES:
* W\ must be low during the block-write cycle.
DQ0–DQ3 are latched on the later of W\ or CAS\ falling edge except in block 6 (see legend).
LEGEND:
1.
2.
3.
4.
5.
6.
Refresh address
Row address
Block address (A2 –A8)
Color-register data
Column-mask data
DQ-mask data. DQ0–DQ3 are latched on the falling edge of RAS\.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
9
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 3: BLOCK-WRITE CIRCUIT BLOCK DIAGRAM
FIGURE 4: EXAMPLE OF BLOCK WRITE OPERATION WITH DQ
MASK AND ADDRESS MASK
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
10
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
TRANSFER OPERATION
• Memory-to-register transfer (pseudo-transfer write).
Transfer operations between the memory arrays (DRAM)
and the data registers (SAM) are invoked by bringing TRG\ low
before RAS\ falls. The states of W\, SE\, and DSF, which are
also latched on the falling edge of RAS\, determine which transfer
operation is invoked. Figure 5 shows an overview of data flow
between the random and the serial interfaces.
As shown in the “Transfer-Operation Functions” table,
the SMJ44C251B/MT42C4256 supports five basic modes of
transfer operation:
• Register-to-memory transfer (normal write transfer,
SAM to DRAM)
• Alternate-write transfer (independent of the state of
SE\)
Switches serial port from serial-out mode to serial-in
mode. No actual data transfer takes place between the
DRAM and the SAM.
• Memory-to-register transfer (normal-read transfer,
transfer entire contents of DRAM row to SAM)
• Split-register-read transfer (divides the SAM into a low
and a high half. Only one half is transferred to the
SAM while the other half is read from the serial I/O port.)
FIGURE 5: BLOCK DIAGRAM SHOWING ONE RANDOM AND ONE
SERIAL-I/O INTERFACE
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
11
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
TRANSFER-OPERATION FUNCTIONS
CAS\
FALL
RAS\ FALL
FUNCTION
Register-to-memory transfer
(normal write transfer)
Alternate-write transfer
(independent of SE\)
Serial-write-mode enable
(pseudo-transfer write)
Memory-to-register transfer
(normal read transfer)
Split-register-read transfer
(must reload tap)
CAS\
TRG\
W\
DSF
SE\
DSF
H
L
L
X
L
X
H
L
L
H
X
X
H
L
L
L
H
X
H
L
H
L
X
X
H
L
H
H
X
X
ADDRESS
RAS\
CAS\
Row
Addr
Row
Addr
Refresh
Addr
Row
Addr
Row
Addr
Tap
Point
Tap
Point
Tap
Point
Tap
Point
Tap
Point
DQ0 - DQ3
RAS\
CAS\
W\
X
X
X
X
X
X
X
X
X
X
LEGEND:
H = High
L = Low
X = Don’t Care
WRITE TRANSFER
All write-transfer cycles (except the pseudo write transfer)
transfer the entire content of SAM to the selected row in the
DRAM. To invoke a write-transfer cycle, W\ must be low when
RAS\ falls. There are three possible write-transfer operations:
normal-write transfer, alternate-write transfer, and pseudo-write
transfer. All write-transfer cycles switch the serial port to the
serial-in mode.
NORMAL-WRITE TRANSFER
(SAM-to-DRAM transfer)
A normal-write transfer cycle loads the contents of the
serial-data register to a selected row in the memory array. TRG\,
W\, and SE\ are brought low and latched at the falling edge of
RAS\. Nine row-address bits (A0–A8) are also latched at the
falling edge of RAS\ to select one of the 512 rows available as
the destination of the data transfer. The nine column-address
bits (A0–A8) are latched at the falling edge of CAS\ to select
one of the 512 tap points in SAM that are available for the next
serial input.
During a write-transfer operation before RAS\ falls, the
serial-input operation must be suspended after a minimum
delay of td(SCRL) but can be resumed after a minimum delay of
td(RHSC) after RAS goes high (see Figure 6).
ALTERNATE-WRITE TRANSFER
(refer to Figure 30)
When DSF is brought high and latched at the falling edge
of RAS\ in the normal-write-transfer cycle, the alternate-write
transfer occurs.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
PSEUDO-WRITE TRANSFER
(write-mode control) (refer to Figure 28)
To invoke the pseudo-write transfer (write-mode control
cycle), SE\ is brought high and latched at the falling edge of
RAS\. The pseudo-write transfer does not actually invoke any
data transfer but switches the mode of the serial port from the
serial-out (read) mode to the serial-in (write) mode.
Before serial data can be clocked into the serial port via the
SDQ terminals and the SC input, the SDQ terminals must be
switched into input mode. Because the transfer does not occur
during the pseudo-transfer write, the row address (A0–A8) is
in the don’t care state and the column address (A0–A8), which
is latched on the falling edge of CAS\, selects one of the 512 tap
points in the SAM that are available for the next serial input.
READ TRANSFER
(DRAM-to-SAM transfer) (refer to Figure 7)
During a read-transfer cycle, data from the selected row in
DRAM is transferred to SAM. There are two read-transfer
operations: normal-read transfer and split-register-read
transfer.
NORMAL-READ TRANSFER
(refer to Figure 7)
The normal-read-transfer operation loads data from a
selected row in DRAM into SAM. TRG\ is brought low and
latched at the falling edge of RAS\. Nine row-address bits
(A0–A8) are also latched at the falling edge of RAS\ to select
one of the 512 rows available for transfer. The nine column(continued)
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12
VRAM
Austin Semiconductor, Inc.
NORMAL-READ TRANSFER
(refer to Figure 7)
address bits (A0– A8) are latched at the falling edge of CAS\ to
select one of the SAM’s 512 available tap points where the
serial data is read out.
SMJ44C251B
MT42C4256
A normal-read transfer can be performed in three ways:
early-load read transfer, real-time or midline-load read transfer,
and late-load read transfer. Each of these offers the flexibility of
controlling the TRG\ trailing edge in the read-transfer cycle
(see Figure 7).
FIGURE 6: NORMAL-WRITE-TRANSFER-CYCLE TIMING
FIGURE 7: NORMAL-READ-TRANSFER TIMINGS
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
13
VRAM
Austin Semiconductor, Inc.
SPLIT-REGISTER-READ TRANSFER
In split-register-read-transfer operation, the serial-data
register is split into halves. The low half contains bits 0–255,
and the high half contains 256–511. While one half is being
read out of the SAM port, the other half can be loaded from the
memory array.
To invoke a split-register read-transfer cycle, DSF is
brought high, TRG\ is brought low, and both are latched at the
falling edge of RAS\. Nine row-address bits (A0–A8) are also
latched at the falling edge of RAS\ to select one of the 512 rows
available for the transfer. The nine column-address bits
(A0–A8) are latched at the falling edge of CAS\, where address
bits A0 –A7 select one of the 255 tap points in the specified half
of SAM and address bit A8 selects which half is to be
transferred. If A8 is a logic low, the low half is transferred. If A8
is a logic high, the high half is transferred. SAM locations 255
and 511 cannot be used as tap points.
SMJ44C251B
MT42C4256
A normal-read transfer must precede the split-register-read
transfer to ensure proper operation. After the normal-readtransfer cycle, the first split-register read transfer can follow
immediately without any minimum SC requirement. However,
there is a minimum requirement of a rising edge of SC between
split-register read-transfer cycles.
QSF indicates which half of the SAM is being accessed
during serial-access operation. When QSF is low, the serialaddress pointer is accessing the lower (least significant) 256
bits of the SAM. When QSF is high, the pointer is accessing
the higher (most significant) 256 bits of the SAM. QSF changes
state upon completing a normal-read-transfer cycle. The tap
point loaded during the current transfer cycle determines the
state of QSF. In split-register read-transfer mode, QSF changes
state when a boundary between the two register halves is
reached (see Figure 8 and Figure 9).
FIGURE 8: EXAMPLE OF A SPLIT-REGISTER READ-TRANSFER
CYCLE AFTER A NORMAL READ-TRANSFER CYCLE
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
14
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
FIGURE 9: A SPLIT-REGISTER READ-TRANSFER CYCLE AFTER A
SPLIT-REGISTER READ-TRANSFER CYCLE
SERIAL-ACCESS OPERATION
The serial-read and serial-write operations can be performed
through the SAM port simultaneously and asynchronously
with DRAM operations except during transfer operations. The
preceding transfer operation determines the input or output
state of the SAM port. If the preceding transfer operation is a
read-transfer operation, the SAM port is in the output mode. If
the preceding transfer operation is a write- or pseudo-writetransfer operation, the SAM port is in the input mode.
Serial data can be read out of or written into SAM by clocking SC starting at the tap point loaded by the preceding transfer
cycle, proceeding sequentially to the most significant bit (bit
511), then wrapping around to the least
significant bit (bit 0) (see Figure 10).
FIGURE 10: SERIAL POINTER DIRECTION FOR SERIAL READ/WRITE
For split-register read-transfer operation, serial data can be read
out from the active half of SAM by clocking SC starting at the
tap point loaded by the preceding split-register-transfer cycle,
then proceeding sequentially to the most significant bit of the
half, bit 255 or bit 511. If there is a split-register-read transfer to
the inactive half during this period, the serial pointer points
next to the tap-point location loaded by that split register (see
Figure 11, Case I). If there is no split-register read transfer to the
inactive half during this period, the serial pointer points next to
bit 256 or bit 0, respectively (see Figure 11, Case II).
FIGURE 11: SERIAL POINTER FOR SPLIT-REGISTER READ
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
15
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
*Stresses greater than those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device. This is
a stress rating only and functional operation of the device at
these or any other conditions above those indicated in the
operation section of this specification is not implied. Exposure
to absolute maximum rating conditions for extended periods
may affect reliability.
ABSOLUTE MAXIMUM RATINGS*
Supply voltage range, VCC1.................................................-1V to 7V
Voltage range on any pin1..................................................-1V to 7V
Short-circuit output current.......................................................50mA
Power dissipation............................................................................1W
Operating free-air temperature range, TA...................-55°C to 125°C
Storage temperature range, TSTG.................................-65°C to 150°C
NOTE:
1. All voltage values are with respect to Vss.
RECOMMENDED OPERATING CONDITIONS
SYM
PARAMETER
MIN
NOM
MAX
UNIT
4.5
5
5.5
V
VCC
Supply Voltage
VSS
Supply Voltage
VIH
High-level input voltage
2.9
6.5
V
VIL
Low-level input voltage**
-1
0.6
V
TA
Operating free-air temperature
-55
125
°C
TC
Operating case temperature
125
°C
NOTE:
0
V
**The algebraic convention, where the more negative (less positive) limit is designated as minimum, is used for logic-voltage levels only.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
16
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
ELECTRICAL CHARACTERISTICS OVER RECOMMENDED RANGES
OF SUPPLY VOLTAGES AND OPERATING FREE-AIR TEMPERATURE
(UNLESS OTHERWISE NOTED)
PARAMETER
SYM
CONDITIONS
MIN
High-level output voltage
VOH
IOH = -5mA
2.4
1
VOL
IOL = 4.2mA
0.4
V
II
VCC = 5V, VI = 0V to 5.8V,
All others open
±10
µA
IO
VCC = 5.5V, VO = 0V to VCC
±10
µA
Low-level output voltage
Input leakage current
2
Output leakage current
-10
MAX
UNIT
V
-12
SYM
CONDITIONS
SAM
PORT
Operating current
ICC1
tc(rd) and tc(W) = MIN
Standby
100
90
mA
Operating current
ICC1A
tc(SC) = MIN
Active
110
100
mA
Standby current
ICC2
All clocks = VCC
Standby
15
15
mA
Standby current
ICC2A
tc(SC) = MIN
Active
35
35
mA
RAS\-only refresh current
ICC3
tc(rd) and tc(W) = MIN
Standby
100
90
mA
RAS\-only refresh current
ICC3A
tc(SC) = MIN
Active
110
100
mA
Page-mode current
ICC4
tc(P) = MIN
Standby
65
60
mA
Page-mode current
ICC4A
tc(SC) = MIN
Active
70
65
mA
CAS\-before-RAS\ current
ICC5
tc(rd) and tc(W) = MIN
Standby
90
80
mA
CAS\-before-RAS\ current
ICC5A
tc(SC) = MIN
Active
110
100
mA
Data-transfer current
ICC6
tc(rd) and tc(W) = MIN
Standby
100
90
mA
Data-transfer current
ICC6A
tc(SC) = MIN
Active
110
100
mA
3
PARAMETER
MIN MAX
MIN MAX UNITS
NOTES:
1. The SMJ44C251B may exhibit simultaneous switching noise as described in the Texas Instruments Advanced CMOS Logic Designer’s Handbook.
This phenomenon is exhibited on the DQ terminals when the SDQ terminals are switched and on the SDQ terminals when the DQ terminals are
switched. This may cause VOL and VOH to exceed the data-book limit for a short period of time, depending upon output loading and temperature. Care
should be taken to provide proper termination, decoupling, and layout of the device to minimize simultaneous switching effects.
2. SE\ is disabled for SDQ output leakage tests.
3. ICC (standby) denotes that the SAM port is inactive (standby) and the DRAM port is active (except for ICC2).
ICCA (active) denotes that the SAM port is active and the DRAM port is active (except for ICC2).
ICC is measured with no load on DQ or SDQ.
4. For conditions shown as MIN/ MAX, use the appropriate value specified in the timing requirements.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
17
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
CAPACITANCE OVER RECOMMENDED RANGES OF SUPPLY
VOLTAGES AND OPERATING FREE-AIR TEMPERATURE, f = 1MHz1
PARAMETER
SYM
MIN
MAX
UNIT
Input capacitance, A0 - A8
Ci(A)
7
pF
Input capacitance, CAS\ and RAS\
Ci(RC)
7
pF
Output capacitance, SDQs and DQs
Co(O)
9
pF
Co(QSF)
9
pF
Output capacitance, SQSF
SWITCHING CHARACTERISTICS OVER RECOMMENDED RANGES
OF SUPPLY VOLTAGES AND OPERATING FREE-AIR TEMPERA-10
-12
TURE2
PARAMETER
SYM/ALT. SYM
Access time from CAS\
CONDITIONS
4
MIN
MAX
MIN
MAX
UNIT
ta(C) /tCAC
td(RLCL) = MAX
25
30
ns
Access time from column address
ta(CA)/tCAA
td(RLCL) = MAX
50
60
ns
Access time from CAS\ high
ta(CP) /tCPA
td(RLCL) = MAX
55
65
ns
Access time from RAS\
ta(R) /tRAC
td(RLCL) = MAX
100
120
ns
Access time of DQ0 - DQ3 from TRG\ low
ta(G) /tOEA
25
30
ns
Access time of SDQ0 - SDQ3 from SC high
t a(SQ) /tSCA
CL = 30pF
30
35
ns
20
25
ns
ta(SE) /tSEA
CL = 30pF
3
tdis(CH) /tOFF
CL = 100pF
0
20
0
20
ns
Disable time, random output from TRG\ high
3
tdis(G) /tOEZ
CL = 100pF
0
20
0
20
ns
3
tdis(SE) /tSEZ
CL = 30pF
0
20
0
20
ns
Access time of SDQ0 - SDQ3 from SE\ low
Disable time, random output from CAS\ high
Disable time, random output from SE\ high
NOTES:
1. Capacitance is sampled only at initial design and after any major change. Samples are tested at 0 V and 25°C with a 1-MHz signal applied to the
terminal under test. All other terminals are open.
2. Switching times assume CL = 100 pF unless otherwise noted (see Figure 12).
3. tdis(CH), tdis(G), and tdis(SE) are specified when the output is no longer driven.
4. For conditions shown as MIN/ MAX, use the appropriate value specified in the timing requirements.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
18
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
TIMING REQUIREMENTS OVER RECOMMENDED RANGES OF
SUPPLY VOLTAGES AND OPERATING FREE-AIR TEMPERATURE1
-10
PARAMETER
Cycle time, read
2
2
Cycle time, write
2
Cycle time, read-modify-write
2
-12
SYM/ALT. SYM
MIN
MAX
MIN
tc(rd)/tRC
190
220
MAX
UNIT
ns
tc(W) /tWC
190
220
ns
tc(rdW) /tRMW
250
290
ns
tc(P) /tPC
60
70
ns
tc(rdWP) /tPRMW
105
125
ns
2
tc(TRD) /tRC
190
220
ns
Cycle time, write transfer
2
tc(TW) /tWC
190
220
ns
2
tc(SC) /tSCC
30
35
ns
Pulse duration, CAS\ high
t w(CH) /tCPN
20
30
ns
4
Pulse duration, CAS\ low
tw(CL)/tCAS
25
Pulse duration, RAS\ high
t w(RH) /tRP
80
Pulse duration, RAS\ low
tw(RL)/tRAS
100
Pulse duration,W\ low
t w(WL) /tWP
25
25
ns
Pulse duration, TRG\ low
t w(TRG)
25
30
ns
Pulse duration, SC high
t w(SCH) /tSC
10
12
ns
Pulse duration, SC low
t w(SCL)/tSCP
10
12
ns
Pulse duration, SE\ low
tw(SEL)/tSE
35
40
ns
Pulse duration, SE\ high
t w(SEH) /tSEP
35
40
ns
t w(GH) /tTP
30
20
ns
t w(RL)P
100
Setup time, column address
tsu(CA)/tASC
0
0
ns
Setup time, DSF before CAS\ low
tsu(SFC) /tFSC
0
0
ns
Setup time, row address
t su(RA)/tASR
0
0
ns
Setup time, W\ before RAS\ low
tsu(WMR) /tWSR
0
0
ns
Setup time, DQ before RAS\ low
t su(DQR) /tMS
0
0
ns
Setup time, TRG\ before RAS\ low
t su(TRG) /tTHS
0
0
ns
6
tsu(SE) /tESR
0
0
ns
t su(SESC) /tSWIS
10
15
ns
Cycle time, page-mode read or write
2
Cycle time, page-mode read-modify-write
Cycle time, read transfer
Cycle time, serial clock
5
Pulse duration, TRG\ high
Pulse duration, RAS\ low (page mode)
Setup time, SE\ before RAS\ low
Setup time, serial write disable
75000
30
75000
90
75000
75000
120
120
ns
ns
75000
75000
ns
ns
Setup time, DSF before RAS\ low
tsu(SFR) /tFSR
0
0
ns
Setup time, data before CAS\ low
t su(DCL)/tDSC
0
0
ns
Setup time, data before W\ low
tsu(DWL)/tDSW
0
0
ns
t su(rd)/tRCS
0
0
ns
Setup time, early write command before CAS\ low
t su(WCL)/tWCS
0
0
ns
Setup time, write before CAS\ high
tsu(WCH) /tCWL
25
30
ns
Setup time, write before RAS\ high with
TRG\ = W\ = low
tsu(WRH) /tRWL
25
30
ns
Setup time, read command
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
19
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
TIMING REQUIREMENTS (continued)1
-10
PARAMETER
-12
SYM/ALT. SYM
MIN
Setup time, SDQ before SC high
t su(SDS) /tSDS
0
0
ns
Hold time, column address after CAS\ low
t h(CLCA)/tCAH
20
20
ns
Hold time, DSF after CAS\ low
t h(SFC) /tCFH
20
20
ns
Hold time, row address after RAS\ low
t h(RA)/tRAH
15
15
ns
Hold time, TRG\ after RAS\ low
th(TRG) /tTLH
15
15
ns
th(SE) /tREH
15
15
ns
th(RWM) /tRWH
15
15
ns
th(RDQ) /tMH
15
15
ns
t h(SFR) /tRFH
15
15
ns
th(RLCA)/tAR
45
45
ns
t h(CLD) /tDH
20
25
ns
th(RLD) /tDHR
45
50
ns
Hold time, SE\ after RAS\ low with
6
TRG\ = W\ = low
Hold time, write mask, transfer enable
after RAS\ low
Hold time, DQ after RAS\ low
(write-mask operation)
Hold time, DSF after RAS\ low
Hold time, column address after RAS\ low
Hold time, data after CAS\ low
7
Hold time, data after RAS\ low
7
MAX
MIN
MAX
UNIT
th(WLD) /tDH
20
25
ns
8
th(CHrd)/tRCH
0
0
ns
8
Hold time, read after RAS\ high
th(RHrd)/tRRH
10
10
ns
Hold time, write after CAS\ low
t h(CLW) /tWCH
30
35
ns
Hold time, data after W\ low
Hold time, read after CAS\ high
7
th(RLW) /tWCR
50
55
ns
9
Hold time, TRG\ after W\ low
th(WLG) /tOEH
25
30
ns
Hold time, SDQ after SC high
t h(SDS) /tSDH
5
5
ns
Hold time, SDQ after SC high
t h(SHSQ) /tSOH
5
5
ns
Hold time, DSF after RAS\ low
t h(RSF) /tFHR
45
45
ns
Hold time, serial-write disable
t h(SCSE) /tSWIH
20
20
ns
Delay time, RAS\ low to CAS\ high
t d(RLCH) /tCSH
100
120
ns
Delay time, CAS\ high to RAS\ low
t d(CHRL)/tCRP
0
0
ns
Delay time, CAS\ low to RAS\ high
t d(CLRH) /tRSH
25
30
ns
td(CLWL)/tCWD
55
65
ns
td(RLCL)/tRCD
25
t d(CARH) /tRAL
50
60
ns
td(RLWL)/tRWD
130
155
ns
td(CAWL)/tAWD
85
100
ns
td(RLCH)RF/tCHR
25
25
ns
td(CLRL)RF/tCSR
10
10
ns
13
td(RHCL)RF/tRPC
Delay time, RAS\ high to CAS\ low
Delay time, CAS\ low to TRG\ high for DRAM read
td(CLGH)
cycles
10
10
ns
25
30
ns
Hold time, write after RAS\ low
Delay time, CAS\ low to W\ low
10,11
Delay time, RAS\ low to CAS\ low
12
Delay time, column address to RAS\ high
Delay time, RAS\ low to W\ low
10
Delay time, column address to W\ low
Delay time, RAS\ low to CAS\ high
Delay time, CAS\ low to RAS\ low
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
13
13
10
75
25
90
ns
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
20
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
TIMING REQUIREMENTS (continued)1
-10
PARAMETER
-12
SYM/ALT. SYM
MIN
t d(GHD) /tOED
25
30
ns
td(RLTH) /tRTH
90
95
ns
td(RLSH) /tRSD
130
140
ns
td(CLSH) /tCSD
40
45
ns
14,15,16
td(SCTR) /tTSL
15
20
ns
15,16
td(THRH) /tTRD
-10
-10
ns
td(SCRL)/tSRS
10
20
ns
td(SCSE)
20
20
ns
Delay time, TRG\ high before data applied at DQ
Delay time, RAS\ low to TRG\ high
(real-time-reload read-transfer cycle only)
Delay time, RAS\ low to first SC high after
14
TRG\ high
Delay time, CAS\ low to first SC high after TRG\
14
high
Delay time, SC high to TRG\ high
Delay time, TRG\ high to RAS\ high
Delay time, SC high to RAS\ low with
6, 17, 18
TRG\ = W\ = low
Delay time, SC high to SE\ high in serial-input
mode
6
MAX
MIN
MAX
UNIT
td(RHSC) /tSRD
25
30
ns
19
td(THRL)/tTRP
tw(RH)
tw(RH)
ns
15, 16
Delay time, TRG\ high to SC high
td(THSC) /tTSD
35
40
ns
20
td(SESC) /tSWS
10
15
ns
td(RHMS)
15
20
ns
td(CLGH) /tCTH
5
5
ns
td(CASH) /tASD
45
50
ns
td(CAGH) /tATH
10
10
ns
td(RLCA)/tRAD
15
Delay time, data to CAS\ low
t d(DCL)/tDZC
0
0
ns
Delay time, data to TRG\ low
td(DGL)/tDZO
0
0
ns
Delay time, RAS\ low to serial-input data
td(RLSD) /tSDD
50
50
ns
Delay time, TRG\ low to RAS\ high
t d(GLRH) /tROH
25
30
ns
td(MSRL)
25
25
ns
Delay time, RAS\ high to SC high
Delay time, TRG\ high to RAS\ low
Delay time, SE\ low to SC high
Delay time, RAS\ high to last (most significant)
rising edge of SC before boundary switch during
split-register read-transfer cycles
Delay time, CAS\ low to TRG\ high in real-time
read-transfer cycles
Delay time, column address to first SC in earlyload read-transfer cycles
Delay time, column address to TRG\ high in realtime read-transfer cycles
Delay time, RAS\ low to column address
12
Delay time, last (most significant) rising edge of
SC to RAS\ low before boundary switch during
split-register read-transfer cycles
Delay time, last (255 or 511) rising edge of SC to
QSF switching a the boundary during split-register
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
ns
40
ns
21
td(CLQSF) /tCQD
35
35
ns
21
td(GHQSF) /tTQD
30
30
ns
21
td(RLQSF) /tRQD
75
75
ns
t rf /tREF
8
8
ms
50
ns
transfer or write-transfer cycles
Delay time, RAS\ low to QSF switching in read-
Transition time
60
40
transfer or write-transfer cycles
Delay time, TRG\ high to QSF switching in read-
Refresh time interval, memory
15
td(SCQSF) /tSQD
21
read transfer cycles
Delay time, CAS\ low to QSF switching in read-
transfer or write-transfer cycles
50
t t/tT
3
50
3
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
21
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
NOTES:
1. Timing measurements are referenced to VIL max and VIH min.
2. All cycle times assume tt = 5 ns.
3. When the odd tap is used (tap address can be 0–511, and odd taps are 1, 3, 5, etc.), the cycle time for SC in the first serial data out cycle needs to
be 70 ns minimum.
4. In a read-modify-write cycle, td(CLWL) and tsu(WCH) must be observed. Depending on the user’s transition times, this may require additional CAS\ low
time [tw(CL) ].
5. In a read-modify-write cycle, td(RLWL) and tsu(WRH) must be observed. Depending on the user’s transition times, this may require additional RAS\ low
time [tw(RL) ].
6. Register-to-memory (write) transfer cycles only
7. The minimum value is measured when td(RLCL) is set to td(RLCL) min as a reference.
8. Either th(RHrd) or t(CHrd) must be satisfied for a read cycle.
9. Output-enable-controlled write. Output remains in the high-impedance state for the entire cycle.
10. Read-modify-write operation only
11. TRG\ must disable the output buffers prior to applying data to the DQ terminals.
12. The maximum value is specified only to assure RAS\ access time.
13. CAS\-before-RAS\ refresh operation only
14. Early-load read-transfer cycle only
15. Real-time-reload read-transfer cycle only
16. Late-load read-transfer cycle only
17. In a read-transfer cycle, the state of SC when RAS\ falls is a don’t care condition. However, to assure proper sequencing of the internal clock
circuitry, there can be no positive transitions of SC for at least 10 ns prior to when RAS\ goes low.
18. In a memory-to-register (read) transfer cycle, td(SCRL) applies only when the SAM was previously in serial-input mode.
19. Memory-to-register (read) and register-to-memory (write) transfer cycles only
20. Serial data-in cycles only
21. Switching times assume CL = 100 pF unless otherwise noted (see Figure 12).
FIGURE 12: LOAD CIRCUIT
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
22
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 13: Read-Cycle Timing
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
23
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
FIGURE 14: Early-Write-Cycle Timing
WRITE-CYCLE STATE TABLE
CYCLE
Write Operation
Write-mask load/use, Write DQs to I/Os
Use previous write mask, Write DQs to I/Os
Load write mask on later of W\ fall and CAS\ fall
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
L
H
H
2
L
L
L
L
STATE
3
4
H
Don't Care
L
Write Mask
L
Don't Care
H
Don't Care
5
Valid Data
Valid Data
Valid Data
Write Mask
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
24
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 15: Delayed-Write-Cycle Timing
(Output-Enable-Controlled Write)
WRITE-CYCLE STATE TABLE
CYCLE
Write Operation
Write-mask load/use, Write DQs to I/Os
Use previous write mask, Write DQs to I/Os
Load write mask on later of W\ fall and CAS\ fall
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
L
H
H
2
L
L
L
L
STATE
3
4
H
Don't Care
L
Write Mask
L
Don't Care
H
Don't Care
5
Valid Data
Valid Data
Valid Data
Write Mask
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
25
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 16: Read-Write/Read-Modify-Write-Cycle Timing
WRITE-CYCLE STATE TABLE
CYCLE
Write Operation
Write-mask load/use, Write DQs to I/Os
Use previous write mask, Write DQs to I/Os
Load write mask on later of W\ fall and CAS\ fall
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
L
H
H
2
L
L
L
L
STATE
3
4
H
Don't Care
L
Write Mask
L
Don't Care
H
Don't Care
5
Valid Data
Valid Data
Valid Data
Write Mask
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
26
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 17: Enhanced-Page-Mode Read-Cycle Timing
NOTES:
1. Access time is ta(CP) or ta(CA) dependent.
2. Output can go from the high-impedance state to an invalid data state prior to the specified access time.
NOTE A: A write cycle or a read-modify-write cycle can be mixed with the read cycles as long as the write and read-modify-write timing specifications
are not violated and the proper polarity of DSF is selected on the falling edges of RAS\ and CAS\ to select the desired write mode (normal,
block write, etc.)
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
27
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 18: Enhanced-Page-Mode Write-Cycle Timing
NOTES:
1. Referenced to CAS or W, whichever occurs last
NOTE B: A read cycle or a read-modify-write cycle can be intermixed with write cycles, observing read and read-modify-write timing specifications.
TRG\ must remain high throughout the entire page-mode operation to assure page-mode cycle time if the late-write feature is used. If the early-writecycle timing is used, the state of TRG\ is a don’t care after the minimum period th(TRG) from the falling edge of RAS\.
WRITE-CYCLE STATE TABLE
CYCLE
Write Operation
Write-mask load/use, Write DQs to I/Os
Use previous write mask, Write DQs to I/Os
Load write mask on later of W\ fall and CAS\ fall
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
L
H
H
2
L
L
L
L
STATE
3
4
H
Don't Care
L
Write Mask
L
Don't Care
H
Don't Care
5
Valid Data
Valid Data
Valid Data
Write Mask
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
28
VRAM
Austin Semiconductor, Inc.
FIGURE 19: Enhanced-Page-Mode
Read-Modify-Write-Cycle Timing
SMJ44C251B
MT42C4256
NOTES:
1. Output can go from the high-impedance state to an invalid data state prior to the specified access time.
NOTE C: A read or a write cycle can be intermixed with read-modify-write cycles as long as the read and write timing specifications are not violated.
WRITE-CYCLE STATE TABLE
CYCLE
Write Operation
Write-mask load/use, Write DQs to I/Os
Use previous write mask, Write DQs to I/Os
Load write mask on later of W\ fall and CAS\ fall
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
L
H
H
2
L
L
L
L
STATE
3
4
H
Don't Care
L
Write Mask
L
Don't Care
H
Don't Care
5
Valid Data
Valid Data
Valid Data
Write Mask
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
29
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 20: Load-Color-Register-Cycle Timing
(Early-Write Load)
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
30
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 21: Load-Color-Register-Cycle Timing
(Delayed-Write Load)
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
31
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 22: Block-Write-Cycle Timing (Early Write)
BLOCK-WRITE-CYCLE STATE TABLE
CYCLE
Write-mask load/use, Block write
Use previous write mask, Block write
Write mask disable, Block write to all I/Os
1
L
H
L
2
L
L
H
Write mask data 0: I/O write disable
1: I/O write enable
Column mask data DQn =
0 column write disable
(n = 0, 1, 2, 3)
1 column write enable
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
STATE
3
4
Write Mask Column Mask
Don't Care Column Mask
Don't Care Column Mask
DQ0 — column 0 (address A1 = 0, A0 = 0)
DQ1 — column 1 (address A1 = 0, A0 = 1)
DQ2 — column 2 (address A1 = 1, A0 = 0)
DQ3 — column 3 (address A1 = 1, A0 = 1)
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
32
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 23: Block-Write-Cycle Timing (Delayed-Write)
BLOCK-WRITE-CYCLE STATE TABLE
CYCLE
Write-mask load/use, Block write
Use previous write mask, Block write
Write mask disable, Block write to all I/Os
Write mask data 0: I/O write disable
1: I/O write enable
Column mask data DQn =
0 column write disable
(n = 0, 1, 2, 3)
1 column write enable
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
1
L
H
L
2
L
L
H
STATE
3
4
Write Mask Column Mask
Don't Care Column Mask
Don't Care Column Mask
DQ0 — column 0 (address A1 = 0, A0 = 0)
DQ1 — column 1 (address A1 = 0, A0 = 1)
DQ2 — column 2 (address A1 = 1, A0 = 0)
DQ3 — column 3 (address A1 = 1, A0 = 1)
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
33
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 24: Enhanced-Page-Mode
Block-Write-Cycle Timing
NOTES:
1. Referenced to CAS\ or W\, whichever occurs last
NOTE D: TRG\ must remain high throughout the entire page-mode operation to assure page-mode cycle time if the late write feature is used. If
the early-write-cycle timing is used, the state of TRG\ is a don’t care after the minimum period th(TRG) from the falling edge of RAS\.
ENHANCED-PAGE-MODE BLOCK-WRITE-CYCLE STATE TABLE
CYCLE
Write-mask load/use, Block write
Use previous write mask, Block write
Write mask disable, Block write to all I/Os
Write mask data 0: I/O write disable
1: I/O write enable
Column mask data DQn =
0 column write disable
(n = 0, 1, 2, 3)
1 column write enable
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
STATE
2
3
4
L
Write Mask Column Mask
L
Don't Care Column Mask
H
Don't Care Column Mask
DQ0 — column 0 (address A1 = 0, A0 = 0)
DQ1 — column 1 (address A1 = 0, A0 = 1)
DQ2 — column 2 (address A1 = 1, A0 = 0)
DQ3 — column 3 (address A1 = 1, A0 = 1)
1
L
H
L
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
34
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 25: RAS\-Only Refresh-Cycle Timing
NOTES:
NOTE E: In persistent write-per-bit function, W\ must be high at the falling edge of RAS\ during the refresh cycle.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
35
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 26: CBR-Refresh-Cycle Timing
NOTES:
NOTE F: In persistent write-per-bit operation, W\ must be high at the falling edge of RAS\ during the refresh cycle.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
36
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 27: Hidden-Refresh-Cycle Timing
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
37
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 28: Write-Mode-Control Pseudo-Transfer Timing
NOTES:
NOTE G: The write-mode-control cycle is used to change the SDQs from the output mode to the input mode. This allows serial data to be written
into the data register. This figure assumes that the device was originally in the serial-read mode.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
38
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 29: Data-Register-to-Memory Transfer Timing,
Serial Input Enable
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
39
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 30: Alternate Data-Register-to-Memory
Transfer-Cycle Timing
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
40
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 31: Memory-to-Data-Register Transfer-Cycle Timing,
Early-Load Operation
NOTES:
NOTE H: Early-load operation is defined as th(TRG) min < th(TRG) < td(RLTH) min.
NOTE I: DQ outputs remain in the high-impedance state for the entire memory-to-data-register transfer cycle. The memory-to-data-register
transfer cycle is used to load the data registers in parallel from the memory array. The 512 locations in each data register are written from the 512
corresponding columns of the selected row. The data that is transferred into the data registers can be either shifted out or transferred back into another
row.
NOTE J: Once data is transferred into the data registers, the SAM is in the serial-read mode (i.e., SQ is enabled), allowing data to be shifted out of the
registers. Also, the first bit to be read from the data register after TRG\ has gone high must be activated by a positive transition of SC.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
41
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 32: Memory-to-Data-Register Transfer-Cycle Timing,
Real-Time-Reload Operation/Late-Load Operation
NOTES:
NOTE K: Late-load operation is defined as td(THRH) < 0 ns.
NOTE L: DQ outputs remain in the high-impedance state for the entire memory-to-data-register transfer cycle. The memory-to-data-register
transfer cycle is used to load the data registers in parallel from the memory array. The 512 locations in each data register are written from the 512
corresponding columns of the selected row. The data that is transferred into the data registers can be either shifted out or transferred back into another
row.
NOTE M: Once data is transferred into the data registers, the SAM is in the serial read mode (i.e., SQ is enabled), allowing data to be shifted out of
the registers. Also, the first bit to be read from the data register after TRG\ has gone high must be activated by a positive transition of SC.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
42
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 33: Memory-to-Data-Register Transfer-Cycle Timing,
SDQ Ports Previously in Serial-Input Mode
NOTES:
NOTE N: Late-load operation is defined as td(THRH) < 0 ns.
NOTE O: DQ outputs remain in the high-impedance state for the entire memory-to-data-register transfer cycle. The memory-to-data-register
transfer cycle is used to load the data registers in parallel from the memory array. The 512 locations in each data register are written from the 512
corresponding columns of the selected row. The data that is transferred into the data registers may be either shifted out or transferred back into
another row.
NOTE P: Once data is transferred into the data registers, the SAM is in the serial read mode (i.e., SQ is enabled), allowing data to be shifted out of
the registers. Also, the first bit to be read from the data register after TRG\ has gone high must be activated by a positive transition of SC.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
43
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 34: Split-Register-Mode Read-Transfer-Cycle Timing
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
44
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 35: Split-Register-Transfer Operating Sequence
NOTES:
NOTE Q: In order to achieve proper split-register operation, a normal read transfer should be performed before the first split-register transfer cycle.
This is necessary to initialize the data register and the starting tap location. First serial access can then begin either after the normal read-transfer
cycle (CASE I), during the first split-register cycle (CASE II), or even after the first split-register transfer cycle (CASE III). There is no minimum
requirement of SC clock between the normal read-transfer cycle and the first split-register cycle.
NOTE R: A split register transfer into the inactive half is not allowed until td(MSRL) is met. td(MSRL) is the minimum delay time between the rising edge
of the serial clock of the last bit (bit 255 or 511) and the falling edge of RAS\ of the split-register transfer cycle into the inactive half. After td(MSRL)
is met, the split-register transfer into the inactive half must also satisfy the td(RHMS) requirement. td(RHMS) is the minimum delay time between the
rising edge of RAS\ of the split-register transfer cycle into the inactive half and the rising edge of the serial clock of the last bit (bit 255 or 511). There
is a minimum requirement of one rising edge of SC clock between two split-register transfer cycles.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
45
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 36: Serial-Write-Cycle Timing (SE\ = VIL)
NOTES:
NOTE S: The serial data-in cycle is used to input serial data into the data registers. Before data can be written into the data registers via the SDQ
terminals, the device must be put into the write mode by performing a write-mode-control (pseudo-transfer) cycle or any other write-transfer cycle.
A read-transfer cycle is the only cycle that takes the serial port (SAM) out of the write mode and puts it into the read mode, disabling the input data.
Data is written starting at the location specified by the input address loaded on the previous transfer cycle.
NOTE T: While accessing data in the serial-data registers, the state of TRG\ is a don’t care as long as TRG\ is held high when RAS\ goes low to prevent
data transfers between memory and data registers.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
46
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 37: Serial-Write-Cycle Timing (SE\-Controlled Write)
NOTES:
NOTE U: The serial data-in cycle is used to input serial data into the data registers. Before data can be written into the data registers via the SDQ
terminals, the device must be put into the write mode by performing a write-mode-control (pseudo-transfer) cycle or any other write-transfer cycle.
A read-transfer cycle is the only cycle that takes the serial port (SAM) out of the write mode and puts it into the read mode, disabling the input data.
Data is written starting at the location specified by the input address loaded on the previous transfer cycle.
NOTE V: While accessing data in the serial-data registers, the state of TRG\ is a don’t care as long as TRG\ is held high when RAS\ goes low to prevent
data transfers between memory and data registers.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
47
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 38: Serial-Read-Cycle Timing (SE\ = VIL)
NOTES:
NOTE W: While reading data through the serial-data register, the state of TRG\ is a don’t care as long as TRG\ is held high when RAS\ goes low. This
is to avoid the initiation of a register-to-memory-to-register data-transfer operation.
NOTE X: The serial data-out cycle is used to read data out of the data registers. Before data can be read via SDQ, the device must be put into the read
mode by performing a transfer-read cycle. Any transfer-write cycles occurring between the transfer-read cycle and the subsequent shifting out of data
take the device out of the read mode and put it in the write mode, not allowing the reading of data.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
48
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
FIGURE 39: Serial-Read-Cycle Timing (SE\-Controlled Read)
NOTES:
NOTE Y: While reading data through the serial-data register, the state of TRG\ is a don’t care as long as TRG\ is held high when RAS\ goes low.
This is to avoid the initiation of a register-to-memory-to-register data-transfer operation.
NOTE Z: The serial data-out cycle is used to read data out of the data registers. Before data can be read via SDQ, the device must be put into the
read mode by performing a transfer-read cycle. Any transfer-write cycles occurring between the transfer-read cycle and the subsequent shifting
out of data take the device out of the read mode and put it in the write mode, not allowing the reading of data.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
49
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
ASI Case #500 (Package Designator DCJ)
SMD 5962-89497, Case Outline T
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
50
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
ASI Case #109 (Package Designator C or JDM)
SMD 5962-89497, Case Outline
X
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
51
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
Package Designator HJM
SMD 5962-89497, Case Outline Y
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
52
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
ASI Case #203 (Package Designator EC or HMM)
SMD 5962-89497, Case Outline Z
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
53
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
Package Designator CZ or SVM
SMD 5962-89497, Case Outline M
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
54
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
MECHANICAL DEFINITIONS*
ASI Case #302 (Package Designator F)
SMD 5962-89497, Case Outline U
SYMBOL
A
b
c
D
E
E1
E2
E3
e
L
Q
S1
SMD SPECIFICATIONS
MIN
MAX
0.090
0.130
0.015
0.022
0.004
0.009
--0.740
0.380
0.420
--0.440
0.180
--0.030
--0.050 BSC
0.250
0.370
0.026
0.045
0.000
---
*All measurements are in inches.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
55
VRAM
SMJ44C251B
MT42C4256
Austin Semiconductor, Inc.
ORDERING INFORMATION
EXAMPLE: MT42C4256DCJ-10/XT
EXAMPLE: MT42C4256C-12/IT
Device
Package
Speed ns Process
Number
Type
MT42C4256
DCJ
-10
/*
MT42C4256
DCJ
-12
/*
Device
Package
Speed ns Process
Number
Type
MT42C4256
C
-10
/*
MT42C4256
C
-12
/*
EXAMPLE: MT42C4256EC-10/883C
EXAMPLE: MT42C4256F-12/XT
Device
Package
Speed ns Process
Number
Type
MT42C4256
EC
-10
/*
MT42C4256
EC
-12
/*
Device
Package
Speed ns Process
Number
Type
MT42C4256
F
-10
/*
MT42C4256
F
-12
/*
EXAMPLE: MT42C4256CZ-12/883C
Device
Package
Speed ns Process
Number
Type
MT42C4256
CZ
-10
/*
MT42C4256
CZ
-12
/*
EXAMPLE: SMJ44C251B 10HJM
EXAMPLE: SMJ44C251B 12JDM
Device
Package
Speed ns
Process
Number
Type
SMJ44C251B
10
HJM
See Note
SMJ44C251B
12
HJM
See Note
Device
Package
Speed ns
Process
Number
Type
SMJ44C251B
10
JDM
See Note
SMJ44C251B
12
JDM
See Note
EXAMPLE: SMJ44C251B 12HMM
EXAMPLE: SMJ44C251B 10SVM
Device
Package
Process
Speed ns
Number
Type
SMJ44C251B
10
HMM
See Note
SMJ44C251B
12
HMM
See Note
Package
Device
Speed ns
Process
Type
Number
SMJ44C251B
10
SVM
See Note
SMJ44C251B
12
SVM
See Note
*OPERATING TEMPERATURE
XT = Military Temperature Range
IT = Industrial Temperature Range
883C = MIL-STD-883C process
-55oC to +125oC
-40°C to +85°C
-55oC to +125oC
NOTE: SMJ prefix denotes MIL-STD-883C process, temperature
range -55oC to +125oC.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
56
VRAM
Austin Semiconductor, Inc.
SMJ44C251B
MT42C4256
ASI TO DSCC PART NUMBER
CROSS REFERENCE*
Package Designator C or JDM
ASI Part Number
SMD Part Number
MT42C4256C-10/883C
5962-8949704MXA
MT42C4256C-12/883C
5962-8949703MXA
SMJ44C251B-10JDM**
5962-8949704MXA
SMJ44C251B-12JDM**
5962-8949703MXA
Package Designator CZ or SVM
ASI Part Number
SMD Part Number
MT42C4256CZ-10/883C
5962-8949704MMA
MT42C4256CZ-12/883C
5962-8949703MMA
SMJ44C251B-10SVM**
5962-8949704MMA
SMJ44C251B-12SVM**
5962-8949703MMA
Package Designator EC or HMM
SMD Part Number
ASI Part Number
MT42C4256EC-10/883C 5962-8949704MZA
MT42C4256EC-12/883C 5962-8949703MZA
SMJ44C251B-10HMM** 5962-8949704MZA
SMJ44C251B-12HMM** 5962-8949703MZA
Package Designator DCJ
ASI Part Number
SMD Part Number
MT42C4256DCJ-10/883C
5962-8949704MTA
MT42C4256DCJ-12/883C
5962-8949703MTA
Package Designator F
SMD Part Number
ASI Part Number
MT42C4256F-10/883C
5962-8949704MUA
MT42C4256F-12/883C
5962-8949703MUA
Package Designator HJM
ASI Part Number
SMD Part Number
SMJ44C251B-10HJM**
5962-8949704MYA
SMJ44C251B-12HJM**
5962-8949703MYA
* ASI part number is for reference only. Orders received referencing the SMD part number will be processed per the SMD.
** Parts are listed on SMD under the old Texas Instruments part number. ASI purchased this product line in November of 1999.
SMJ44C251B/MT42C4256
Rev. 0.1 12/03
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
57