UPSD3234AV-24U1T STMicroelectronics, UPSD3234AV-24U1T Datasheet - Page 104

• Manufacturer Part Number: UPSD3234AV-24U1T
• Description: Flash Programmable System Devices with 8032 Microcontroller Core and 64Kbit SRAM
• Manufacturer: STMicroelectronics

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uPSD3234A, uPSD3234BV, uPSD3233B, uPSD3233BV
Programming Flash Memory
Flash memory must be erased prior to being pro-
grammed. A byte of Flash memory is erased to all
'1s' (FFh), and is programmed by setting selected
bits to '0.' The MCU may erase Flash memory all
at once or by-sector, but not byte-by-byte. Howev-
er, the MCU may program Flash memory byte-by-
byte.
The primary and secondary Flash memories re-
quire the MCU to send an instruction to program a
byte or to erase sectors (see
Once the MCU issues a Flash memory Program or
Erase instruction, it must check for the status bits
for completion. The embedded algorithms that are
invoked support several means to provide status
to the MCU. Status may be checked using any of
three methods: Data Polling, Data Toggle, or
Ready/Busy (PC3).
Data Polling. Polling on the Data Polling Flag Bit
(DQ7) is a method of checking whether a Program
or Erase cycle is in progress or has completed.
Figure
When the MCU issues a Program instruction, the
embedded algorithm begins. The MCU then reads
the location of the byte to be programmed in Flash
memory to check status. The Data Polling Flag Bit
(DQ7) of this location becomes the complement of
b7 of the original data byte to be programmed. The
MCU continues to poll this location, comparing the
Data Polling Flag Bit (DQ7) and monitoring the Er-
ror Flag Bit (DQ5). When the Data Polling Flag Bit
(DQ7) matches b7 of the original data, and the Er-
ror Flag Bit (DQ5) remains '0,' the embedded algo-
rithm is complete. If the Error Flag Bit (DQ5) is '1,'
the MCU should test the Data Polling Flag Bit
(DQ7) again since the Data Polling Flag Bit (DQ7)
may have changed simultaneously with the Error
Flag Bit (DQ5) (see Figure 52).
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
104/170
52
shows the Data Polling algorithm.
Table 85., page
101).
byte that was written to the Flash memory with the
byte that was intended to be written.
When using the Data Polling method during an
Erase cycle, Figure
Data Polling Flag Bit (DQ7) is '0' until the Erase cy-
cle is complete. A '1' on the Error Flag Bit (DQ5) in-
dicates a time-out condition on the Erase cycle; a
'0' indicates no error. The MCU can read any loca-
tion within the sector being erased to get the Data
Polling Flag Bit (DQ7) and the Error Flag Bit
(DQ5).
PSDsoft Express generates ANSI C code func-
tions which implement these Data Polling algo-
rithms.
Figure 52. Data Polling Flowchart
at VALID ADDRESS
NO
READ DQ5 & DQ7
READ DQ7
START
52
DATA
DATA
DQ7
DQ5
DQ7
FAIL
= 1
=
=
still applies. However, the
YES
NO
NO
YES
YES
PASS
AI01369B