參數(shù)資料
型號(hào)： A45L9332AE-8
廠商： AMIC Technology Corporation
英文描述： 256K X 32 Bit X 2 Banks Synchronous Graphic RAM
中文描述： 256 × 32位× 2銀行同步圖形內(nèi)存
文件頁(yè)數(shù)： 16/55頁(yè)
文件大?。?/td> 1255K
代理商： A45L9332AE-8
Device Operations (continued)
A45L9332A Series
PRELIMINARY
(October, 2001, Version 0.1)
15
AMIC Technology, Inc.
Bank Activate
The bank activate command is used to select a random row
in an idle bank. By asserting low on
RAS
and
CS
with
desired row and bank addresses, a row access is initiated.
The read or write operation can occur after a time delay of
t
RCD
(min) from the time of bank activation. t
RCD
(min) is an
internal timing parameter of SGRAM, therefore it is
dependent on operating clock frequency. The minimum
number of clock cycles required between bank activate and
read or write command should be calculated by dividing
t
RCD
(min) with cycle time of the clock and then rounding off
the result to the next higher integer. The SGRAM has two
internal banks on the same chip and shares part of the
internal circuitry to reduce chip area, therefore it restricts
the activation of both banks immediately. Also the noise
generated during sensing of each bank of SGRAM is high
requiring some time for power supplies recover before the
other bank can be sensed reliably. t
RRD
(min) specifies the
minimum time required between activating different banks.
The number of clock cycles required between different bank
activation must be calculated similar to t
RCD
specification.
The minimum time required for the bank to be active to
initiate sensing and restoring the complete row of dynamic
cells is determined by t
RAS
(min) specification before a
precharge command to that active bank can be asserted.
The maximum time any bank can be in the active state is
determined by t
RAS
(max). The number of cycles for both
t
RAS
(min) and t
RAS
(max) can be calculated similar to t
RCD
specification.
Burst Read
The burst read command is used to access burst of data on
consecutive clock cycles from an active row in an active
bank. The burst read command is issued by asserting low
on
CS
and
CAS
with
WE
being high on the positive edge
of the clock. The bank must be active for at least t
RCD
(min)
before the burst read command is issued. The first output
appears CAS latency number of clock cycles after the issue
of burst read command. The burst length, burst sequence
and latency from the burst read command is determined by
the mode register which is already programmed. The burst
read can be initiated on any column address of the active
row. The address wraps around if the initial address does
not start from a boundary such that number of outputs from
each I/O are equal to the burst length programmed in the
mode register. The output goes into high-impedance at the
end of the burst, unless a new burst read was initiated to
keep the data output gapless. The burst read can be
terminated by issuing another burst read or burst write in
the same bank or the other active bank or a precharge
command to the same bank. The burst stop command is
valid only at full page burst length where the output dose
not go into high impedance at the end of burst and the
burst is wrap around.
Burst Write
The burst write command is similar to burst read command,
and is used to write data into the SGRAM consecutive clock
cycles in adjacent addresses depending on burst length
and burst sequence. By asserting low on
CS
,
CAS
and
WE
with valid column address, a write burst is initiated.
The data inputs are provided for the initial address in the
same clock cycle as the burst write command. The input
buffer is deselected at the end of the burst length, even
though the internal writing may not have been completed
yet. The writing can not complete to burst length. The burst
write can be terminated by issuing a burst read and DQM
for blocking data inputs or burst write in the same or the
other active bank. The burst stop command is valid only at
full page burst length where the writing continues at the end
of burst and the burst is wrap around. The write burst can
also be terminated by using DQM for blocking data and
precharging the bank “t
RDL
” after the last data input to be
written into the active row. See DQM OPERATION also.
DQM Operation
The DQM is used to mask input and output operation. It
works similar to
OE
during read operation and inhibits
writing during write operation. The read latency is two
cycles from DQM and zero cycle for write, which means
DQM masking occurs two cycles later in the read cycle and
occurs in the same cycle during write cycle. DQM operation
is synchronous with the clock, therefore the masking occurs
for a complete cycle. The DQM signal is important during
burst interrupts of write with read or precharge in the
SGRAM. Due to asynchronous nature of the internal write,
the DQM operation is critical to avoid unwanted or
incomplete writes when the complete burst write is not
required. DQM is also used for device selection, byte
selection and bus control in a memory system. DQM0
controls DQ0 to DQ7, DQM1 controls DQ8 to DQ15, DQM2
controls DQ16 to DQ23, DQM3 controls DQ24 to DQ31.
DQM masks the DQ’s by a byte regardless that the
corresponding DQ’s are in a state of WPB masking or Pixel
masking. Please refer to DQM timing diagram also.
Precharge
The precharge operation is performed on an active bank by
asserting low on
CS
,
RAS
,
WE
and A9 with valid A10 of
the bank to be precharged. The precharge command can
be asserted anytime after t
RAS
(min) is satisfied from the
bank activate command in the desired bank. “t
RP
” is defined
as the minimum time required to precharge a bank.
The minimum number of clock cycles required to complete
row precharge is calculated by dividing “t
RP
” with clock cycle
time and rounding up to the next higher integer. Care
should be taken to make sure that burst write is completed
or DQM is used to inhibit writing before precharge
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