参数资料
型号: W981216DH-75
厂商: WINBOND ELECTRONICS CORP
元件分类: DRAM
英文描述: 8M X 16 SYNCHRONOUS DRAM, 5.4 ns, PDSO54
封装: 0.400 INCH, 0.80 MM PITCH, TSOP2-54
文件页数: 6/44页
文件大小: 1221K
代理商: W981216DH-75
W981216DH / W9812G6DH
- 14 -
12.4 Read and Write Access Modes
After a bank has been activated, a read or write cycle can be followed. This is accomplished by setting
RAS high and CAS low at the clock rising edge after minimum of tRCD delay. WE pin voltage level
defines whether the access cycle is a read operation (WE high), or a write operation (WE low). The
address inputs determine the starting column address.
Reading or writing to a different row within an activated bank requires the bank be precharged and a
new Bank Activate command be issued. When more than one bank is activated, interleaved bank
Read or Write operations are possible. By using the programmed burst length and alternating the
access and precharge operations between multiple banks, seamless data access operation among
many different pages can be realized. Read or Write Commands can also be issued to the same bank
or between active banks on every clock cycle.
12.5 Burst Read Command
The Burst Read command is initiated by applying logic low level to CS and CAS while holding RAS
and WE high at the rising edge of the clock. The address inputs determine the starting column
address for the burst. The Mode Register sets type of burst (sequential or interleave) and the burst
length (1, 2, 4, 8, full page) during the Mode Register Set Up cycle. Table 2 and 3 in the next page
explain the address sequence of interleave mode and sequential mode.
12.6 Burst Write Command
The Burst Write command is initiated by applying logic low level to CS, CAS and WE while holding
RAS high at the rising edge of the clock. The address inputs determine the starting column address.
Data for the first burst write cycle must be applied on the DQ pins on the same clock cycle that the
Write Command is issued. The remaining data inputs must be supplied on each subsequent rising
clock edge until the burst length is completed. Data supplied to the DQ pins after burst finishes will be
ignored.
12.7 Read Interrupted by a Read
A Burst Read may be interrupted by another Read Command. When the previous burst is interrupted,
the remaining addresses are overridden by the new read address with the full burst length. The data
from the first Read Command continues to appear on the outputs until the CAS latency from the
interrupting Read Command the is satisfied.
12.8 Read Interrupted by a Write
To interrupt a burst read with a Write Command, DQM may be needed to place the DQs (output
drivers) in a high impedance state to avoid data contention on the DQ bus. If a Read Command will
issue data on the first and second clocks cycles of the write operation, DQM is needed to insure the
DQs are tri-stated. After that point the Write Command will have control of the DQ bus and DQM
masking is no longer needed.
12.9 Write Interrupted by a Write
A burst write may be interrupted before completion of the burst by another Write Command. When the
previous burst is interrupted, the remaining addresses are overridden by the new address and data
will be written into the device until the programmed burst length is satisfied.
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