參數(shù)資料
型號: TMS28F400BZT90BDBJE
廠商: Texas Instruments, Inc.
英文描述: 8-BIT/262144 BY 16-BIT BOOT-BLOCK FLASH MEMORIES
中文描述: 8-BIT/262144由16位啟動塊閃存
文件頁數(shù): 10/29頁
文件大小: 404K
代理商: TMS28F400BZT90BDBJE
TMS28F400BZT, TMS28F400BZB
524288 BY 8-BIT/262144 BY 16-BIT
BOOT-BLOCK FLASH MEMORIES
SMJS400E – JUNE 1994 – REVISED JANUARY 1998
10
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
normal programming
There are two CSM commands for programming: program setup and alternate program setup
(see Table 1). After the desired command code is entered, the WSM takes over and correctly sequences the
device to complete the program operation. During this time, the CSM responds only to status reads until the
program operation has been completed, after which all commands to the CSM become valid again. Once a
program command has been issued, the WSM cannot normally be interrupted until the program algorithm has
been completed (see Figure 3 and Figure 4). Taking RP to V
IL
during programming aborts the program
operation. During programming, V
PP
must remain at V
PPH
. Only 0s are written and compared during a program
operation. If 1s are programmed, the memory cell contents do not change and no error occurs.
A program-setup command can be aborted by writing FFh (in byte-wide mode) or FFFFh (in word-wide mode)
during the second cycle. After writing all 1s during the second cycle, the CSM responds only to status reads.
When the WSM status bit (SB7) is set to a logic-high level, signifying the nonprogram operation is terminated,
all commands to the CSM become valid again.
erase operations
There are two erase operations that can be performed by the TMS28F400BZx devices: block erase and erase
suspend/erase resume. An erase operation must be used to initialize all bits in an array block to 1s. After
block-erase confirm is issued, the CSM responds only to status reads or erase-suspend commands until the
WSM completes its task.
Block erasure
Block erasure inside the memory array sets all bits within the addressed block to logic 1s. Erasure is
accomplished only by blocks; data at single address locations within the array cannot be individually erased.
The block to be erased is selected by using any valid address within that block. RP must be at V
HH
for
changing the data content of the boot block. Block erasure is initiated by a command sequence to the CSM:
block-erase setup (20h) followed by block-erase confirm (D0h) (see Figure 5). A two-command erase
sequence protects against accidental erasure of memory contents.
Erase setup and confirm commands are latched on the rising edge of E or W, whichever occurs first. Block
addresses are latched during the block-erase-confirm command on the rising edge of E or W (see Figure 10
and Figure 11). When the block-erase-confirm command is complete, the WSM automatically executes a
sequence of events to complete the block erasure. During this sequence, the block is programmed with
logic 0s, data is verified, all bits in the block are erased, and finally, verification is performed to ensure that all
bits are correctly erased. Monitoring of the erase operation is possible through the status register (see the
subsection, “read status register”).
Erase suspend/erase resume
During the execution of an erase operation, the erase-suspend command (B0h) can be entered to direct the
WSM to suspend the erase operation. Once the WSM has reached the suspend state, it allows the CSM to
respond only to the read-array, read-status-register, and erase-resume commands. During the
erase-suspend operation, array data should be read from a block other than the one being erased. To
resume the erase operation, an erase-resume command (D0h) must be issued to cause the CSM to clear
the suspend state previously set (see Figure 5 and Figure 6).
automatic power-saving mode
Substantial power savings are realized during periods when the array is not being read. During this time, the
device switches to the automatic power-saving (APS) mode. When the device switches to this mode, I
CC
is
typically reduced from 40 mA to 1 mA (I
OUT
= 0 mA). The low level of power is maintained until another read
operation is initiated. In this mode, the I/O pins retain the data from the last memory-address read until a new
address is read. This mode is entered automatically if no address or control pins toggle within a 200-ns time-out
period. At least one transition on E must occur after power up to activate this mode.
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