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M52D128168A-7TG 参数 Datasheet PDF下载

M52D128168A-7TG图片预览
型号: M52D128168A-7TG
PDF下载: 下载PDF文件 查看货源
内容描述: 2M ×16位×4手机银行同步DRAM [2M x 16 Bit x 4 Banks Mobile Synchronous DRAM]
分类和应用: 存储内存集成电路光电二极管动态存储器手机
文件页数/大小: 48 页 / 1178 K
品牌: ESMT [ ELITE SEMICONDUCTOR MEMORY TECHNOLOGY INC. ]
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ESMT  
M52D128168A  
DEVICE OPERATIONS (Continued)  
BANK ACTIVATE  
and burst sequence. By asserting low on CS , CAS  
The bank activate command is used to select a random row  
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 can be  
completed yet. The writing can be complete by issuing a  
burst read and DQM for blocking data inputs or burst  
write in the same or another active bank. The burst stop  
command is valid at every burst length. The write burst  
can also be terminated by using DQM for blocking data  
and procreating the bank tRDL after the last data input to  
be written into the active row. See DQM OPERATION  
also.  
in an idle bank. By asserting low on RAS and CS with  
desired row and bank address, a row access is initiated. The  
read or write operation can occur after a time delay of tRCD  
(min) from the time of bank activation. tRCD is the internal  
timing parameter of SDRAM, 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 tRCD (min) with  
cycle time of the clock and then rounding of the result to the  
next higher integer. The SDRAM has four internal banks in  
the same chip and shares part of the internal circuitry to  
reduce chip area, therefore it restricts the activation of four  
banks simultaneously. Also the noise generated during  
sensing of each bank of SDRAM is high requiring some time  
for power supplies to recover before another bank can be  
sensed reliably. tRRD (min) specifies the minimum time  
required between activating different bank. The number of  
clock cycles required between different bank activation must  
be calculated similar to tRCD 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  
tRAS (min). Every SDRAM bank activate command must  
satisfy tRAS (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 tRAS (max)  
and tRAS (max) can be calculated similar to tRCD specification.  
DQM OPERATION  
The DQM is used mask input and output operations. It  
works similar to OE during 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 read cycle and  
occurs in the same cycle during write cycle. DQM  
operation is synchronous with the clock. The DQM  
signal is important during burst interrupts of write with  
read or precharge in the SDRAM. 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 required. Please refer to DQM  
timing diagram also.  
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  
PRECHARGE  
The precharge is performed on an active bank by  
asserting low on clock cycles required between bank  
activate and clock cycles required between bank  
CS and RAS with WE being high on the positive edge  
of the clock. The bank must be active for at least tRCD (min)  
before the burst read command is issued. The first output  
appears in 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 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 at every page burst length.  
activate and CS , RAS , WE and A10/AP with valid  
BA0~BA1 of the bank to be procharged. The precharge  
command can be asserted anytime after tRAS (min) is  
satisfy from the bank active command in the desired  
bank. tRP is defined as the minimum number of clock  
cycles required to complete row precharge is calculated  
by dividing tRP 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 command is asserted.  
The maximum time any bank can be active is specified  
by tRAS (max). Therefore, each bank activate command.  
At the end of precharge, the bank enters the idle state  
and is ready to be activated again. Entry to power-down,  
Auto refresh, Self refresh and Mode register set etc. is  
possible only when all banks are in idle state.  
BURST WRITE  
The burst write command is similar to burst read command  
and is used to write data into the SDRAM on consecutive  
clock cycles in adjacent addresses depending on burst  
length  
Elite Semiconductor Memory Technology Inc.  
Publication Date: Aug. 2009  
Revision: 1.3  
12/48  
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