km4132g271b Samsung Semiconductor, Inc., km4132g271b Datasheet - Page 17

• Manufacturer Part Number: km4132g271b
• Description: 128k X 32bit X 2 Banks Synchronous Graphic Ram Lvttl
• Manufacturer: Samsung Semiconductor, Inc.

KM4132G271B
DEVICE OPERATIONS (Continued)
WRITE PER BIT
selectively masks bits of data being written to the devices. The
mask is stored in an internal register and applied to each bit of
data written when the mask is enabled. Bank active command
with DSF=High enables write per bit for associated bank. Bank
active command with DSF=Low disables write per bit for the
associated bank. The mask used for write per bit operations is
stored in the mask register accessed by SWCBR(Special Mode
Register Set Command). When a mask bit=1, the associated
data bit is written when a write command is executed and write
per bit has been enabled for the bank being written. When a
mask bit=0, the associated data bit is unaltered when a write
command is executed and the write per bit has been enabled for
the bank being written. No additional timing conditions are
required for write per bit operations. Write per bit writes can be
either single write, burst writes or block writes. DQM masking is
the same for write per bit and non-WPB write.
BLOCK WRITE
consecutive 8 columns of data within a RAM device during a sin-
gle access cycle. During block write the data to be written comes
from an internal "color" register and DQ I/O pins are used for
independent column selection. The block of column to be written
is aligned on 8 column boundaries and is defined by the column
address with the 3 LSB s ignored. Write command with DSF=1
enables block write for the associated bank. A write command
with DSF=0 enables normal write for the associated bank. The
block width is 8 column where column="n" bits for by "n" part.
The color register is the same width as the data port of the
chip.It is written via a SWCBR where data present on the DQ pin
is to be coupled into the internal color register. The color register
provides the data masked by the DQ column select, WPB
mask(If enabled), and DQM byte mask. Column data mask-
ing(Pixel masking) is provided on an individual column basis for
each byte of data. The column mask is driven on the DQ pins
during a block write command. The DQ column mask function is
segmented on a per bit basis(i.e. DQ[0:7] provides the column
mask for data bits[0:7], DQ[8:15] provides the column mask for
data bits[8:15], DQ0 masks column[0] for data bits[0:7], DQ9
masks column [1] for data bits [8:15], etc). Block writes are
always non-burst, independent of the burst length that has been
programmed into the mode register. Back to back block writes
are allowed provided that the specified block write cycle
time(
active command with DSF=1, then write per bit masking of the
color register data is enabled.
If write per bit was disabled by a bank active command with
DSF=0, the write per bit masking of the color register data is dis-
abled. DQM masking provides independent data byte masking
during block write exactly the same as it does during normal
write operations, except that the control is extended to the con-
secutive 8 columns of the block write.
Write per bit(i.e. I/O mask mode) for SGRAM is a function that
Block write is a feature allowing the simultaneous writing of
t
BWC
) is satisfied. If write per bit was enabled by the bank
- 17
Timing Diagram to lllustrate
CLOCK
CKE
CS
RAS
CAS
WE
DSF
0
1 CLK BW
HIGH
1
Rev. 2.4 (May 1998)
CMOS SGRAM
2
t
BWC