參數(shù)資料
型號(hào): PSD813F2A-15JI
廠商: STMICROELECTRONICS
元件分類: 微控制器/微處理器
英文描述: 128K X 8 FLASH, 27 I/O, PIA-GENERAL PURPOSE, PQCC52
封裝: PLASTIC, LCC-52
文件頁數(shù): 30/110頁
文件大小: 837K
代理商: PSD813F2A-15JI
PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2
26/110
Data Toggle
Checking the Toggle Flag Bit (DQ6) is a method of
determining whether a Program or Erase cycle is
in progress or has completed. Figure 8 shows the
Data Toggle algorithm.
When the MCU issues a Program instruction, the
embedded algorithm within the PSD begins. The
MCU then reads the location of the byte to be pro-
grammed in Flash memory to check status. The
Toggle Flag Bit (DQ6) of this location toggles each
time the MCU reads this location until the embed-
ded algorithm is complete. The MCU continues to
read this location, checking the Toggle Flag Bit
(DQ6) and monitoring the Error Flag Bit (DQ5).
When the Toggle Flag Bit (DQ6) stops toggling
(two consecutive reads yield the same value), and
the Error Flag Bit (DQ5) remains ’0,’ the embed-
ded algorithm is complete. If the Error Flag Bit
(DQ5) is '1,' the MCU should test the Toggle Flag
Bit (DQ6) again, since the Toggle Flag Bit (DQ6)
may have changed simultaneously with the Error
Flag Bit (DQ5, see Figure 8).
The Error Flag Bit (DQ5) is set if either an internal
time-out occurred while the embedded algorithm
attempted to program the byte, or if the MCU at-
tempted to program a '1' to a bit that was not
erased (not erased is logic '0').
It is suggested (as with all Flash memories) to read
the location again after the embedded program-
ming algorithm has completed, to compare the
byte that was written to Flash memory with the
byte that was intended to be written.
When using the Data Toggle method after an
Erase cycle, Figure 8 still applies. the Toggle Flag
Bit (DQ6) toggles until the Erase cycle is complete.
A '1' on the Error Flag Bit (DQ5) indicates a time-
out condition on the Erase cycle; a '0' indicates no
error. The MCU can read any location within the
sector being erased to get the Toggle Flag Bit
(DQ6) and the Error Flag Bit (DQ5).
PSDsoft Express generates ANSI C code func-
tions which implement these Data Toggling algo-
rithms.
Unlock Bypass (PSD833F2x, PSD834F2x,
PSD853F2x, PSD854F2x)
The Unlock Bypass instructions allow the system
to program bytes to the Flash memories faster
than using the standard Program instruction. The
Unlock Bypass mode is entered by first initiating
two Unlock cycles. This is followed by a third
WRITE cycle containing the Unlock Bypass code,
20h (as shown in Table 9., page 21).
The Flash memory then enters the Unlock Bypass
mode. A two-cycle Unlock Bypass Program in-
struction is all that is required to program in this
mode. The first cycle in this instruction contains
the Unlock Bypass Program code, A0h. The sec-
ond cycle contains the program address and data.
Additional data is programmed in the same man-
ner. These instructions dispense with the initial
two Unlock cycles required in the standard Pro-
gram instruction, resulting in faster total Flash
memory programming.
During the Unlock Bypass mode, only the Unlock
Bypass Program and Unlock Bypass Reset Flash
instructions are valid.
To exit the Unlock Bypass mode, the system must
issue the two-cycle Unlock Bypass Reset Flash in-
struction. The first cycle must contain the data
90h; the second cycle the data 00h. Addresses are
Don’t Care for both cycles. The Flash memory
then returns to READ Mode.
Figure 8. Data Toggle Flowchart
READ
DQ5 & DQ6
START
READ DQ6
FAIL
PASS
AI01370B
DQ6
=
TOGGLE
NO
YES
DQ5
= 1
NO
YES
DQ6
=
TOGGLE
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