AN1496 - APPLICATION NOTE

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1 - INTRODUCTION TO ST10 0.35

µm EMBEDDED FLASH

This chapter is describing the improvements made from the ST10F168 and the differences with

stand-alone Flash memories.

1.1 - Differences with ST10F168

1.1.1 - Single Supply

ST10 variants with 0.35

µm embedded Flash do not require specific programming supply. On-chip charge

pumps will provide with the necessary programming supply from the external single 5 volt supply.

1.1.2 - New Erase/Program Controller

The 0.35

µm Erase/Program Controller has been changed to be closer to the one of stand-alone Flash

memories : erasing and programming of Flash memory cells is no more done by the ST10. This allows :

– Savings on system stack : there is no more need to allocate space on the ST10 system stack for eras-

ing and programming,

– Improved efficiency during programming : ST10 CPU can be used to handle communication during

the time where the Erase/Program Controller is dealing with the Flash,

– Improved clock scheme : the Flash erase/program controller has its own clock; there is no more need

to specify it the CPU clock. This also simplifies the handling of special events (like PLL unlock) during

erasing/programming.

1.1.3 - Improved Granularity of Block Sizes

ST10 0.35

µm embedded Flash has improved block granulaty (smaller blocks) and also features boot

block organisation :

– Block size is 64 Kbyte for standard blocks,

– Small blocks for the 4 boot blocks (16 Kbyte, then 8 Kbyte, 8 Kbyte, 32 Kbyte).

1.2 - Comparison with Stand-alone Flash Memories

1.2.1 - Similar But Different Erase/Program Commands

The Erase/program Controller of ST10F269/F280 is derived from the Common Flash memory Interface :

– To keep the same level of proven safety, the special sequence of commands of stand alone Flash mem-

ories has been kept,

– To differentiate from external Flash memories, the value of the commands (address and data) have

been slighlty modified.

This allows to re-use existing software written for stand-alone Flash memories with few modifications. The

following chapters describe them.

1.2.2 - Description of the Commands to the Flash Controller

The following table is describing the possible commands with ST10F269/F280 Erase/Program Controller.

Commands to the Flash are defined by a sequence of ST10 write cycles with specific addresses and data

within the Flash memory range. The length of the sequence varies from 1 cycle (ex : Read/Reset) to 6

cycles (chip erase).

Block erase command can be extended by 1 cycle per additional block to erase. This translates in a

maximum of 12 cycles for ST10F269 and of 16 cycles for ST10F280.