參數(shù)資料
型號(hào): μPD4564323
廠商: NEC Corp.
英文描述: 64M-bit Synchronous DRAM(64M 同步動(dòng)態(tài)RAM)
中文描述: 6400位同步DRAM(6400同步動(dòng)態(tài)RAM)的
文件頁(yè)數(shù): 23/82頁(yè)
文件大小: 659K
代理商: ΜPD4564323
23
μ
PD4564323
Preliminary Data Sheet
9. Precharge
The precharge command can be issued anytime after t
RAS (MIN.)
is satisfied.
Soon after the precharge command is issued, precharge operation performed and the synchronous DRAM enters
the idle state after t
RP
is satisfied. The parameter t
RP
is the time required to perform the precharge.
The earliest timing in a read cycle that a precharge command can be issued without losing any data in the burst is
as follows.
It is depending on the /CAS latency and clock cycle time.
T0
T1
T2
T3
T4
T5
T6
T7
Burst length=4
Read
Read
Q1
Q2
Q3
Q4
PRE
Hi-Z
Q1
Q2
Q3
Q4
PRE
Hi-Z
(t
RAS
must be satisfied)
CLK
Command
/CAS latency = 2
DQ
Command
/CAS latency = 3
DQ
T8
In order to write all data to the memory cell correctly, the asynchronous parameter “t
DPL
” must be satisfied. The
t
DPL(MIN.)
specification defines the earliest time that a precharge command can be issued. Minimum number of clocks
is calculated by dividing t
DPL(MIN.)
with clock cycle time.
In summary, the precharge command can be issued relative to reference clock that indicates the last data word is
valid. In the following table, minus means clocks before the reference; plus means time after the reference.
/CAS latency
Read
Write
2
–1
+t
DPL (MIN.)
3
–2
+t
DPL (MIN.)
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