
Obsolete
Product(s)
- Obsolete
Product(s)
UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV
Memory blocks
Typically, the MCU can read Flash memory using READ operations, just as it would read a
ROM device. However, Flash memory can only be altered using specific Erase and Program
instructions. For example, the MCU cannot write a single byte directly to Flash memory as it
would write a byte to RAM. To program a byte into Flash memory, the MCU must execute a
Program instruction, then test the status of the Program cycle. This status test is achieved
by a READ operation or polling Ready/Busy (PC3).
22.3
Instructions
An instruction consists of a sequence of specific operations. Each received byte is
sequentially decoded by the PSD module and not executed as a standard WRITE operation.
The instruction is executed when the correct number of bytes are properly received and the
time between two consecutive bytes is shorter than the time-out period. Some instructions
are structured to include READ operations after the initial WRITE operations.
The instruction must be followed exactly. Any invalid combination of instruction bytes or
time-out between two consecutive bytes while addressing Flash memory resets the device
logic into READ mode (Flash memory is read like a ROM device).
The Flash memory supports the instructions summarized in
Table 85:●
Erase memory by chip or sector
●
Suspend or resume sector erase
●
Program a Byte
●
RESET to READ mode
●
Read Sector Protection Status
●
Bypass
These instructions are detailed in
Table 85. For efficient decoding of the instructions, the first
two bytes of an instruction are the coded cycles and are followed by an instruction byte or
confirmation byte. The coded cycles consist of writing the data AAh to address X555h
during the first cycle and data 55h to address XAAAh during the second cycle. Address
signals A15-A12 are Don’t Care during the instruction WRITE cycles. However, the
appropriate Sector Select (FS0-FS7 or CSBOOT0-CSBOOT3) must be selected.
The primary and secondary Flash memories have the same instruction set (except for Read
Primary Flash Identifier). The Sector Select signals determine which Flash memory is to
receive and execute the instruction. The primary Flash memory is selected if any one of
Sector Select (FS0-FS7) is High, and the secondary Flash memory is selected if any one of
Sector Select (CSBOOT0-CSBOOT3) is High.
Table 85.
Instructions
Instruction
FS0-FS7 or
CSBOOT0-
CSBOOT3
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5
Cycle 6
Cycle 7
READ(5)
1
“Read”
RD @ RA
READ Sector
Protection(6,8,13)
1
AAh@
X555h
55h@
XAAAh
90h@
X555h
Read
status @
XX02h