ST10F269Z2QX datasheet(31/161 Pages) STMICROELECTRONICS

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ST10F269Z2Qx

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When the ST10F269Z2Qx has entered BSL mode, the following configuration is automatically set (values

that deviate from the normal reset values, are

marked):

In this case, the watchdog timer is disabled, so the

bootstrap loading sequence is not time limited.

Pin TXD0 is configured as output, so the

ST10F269Z2Qx can return the identification Byte.

Even if the internal Flash is enabled, no code can

be executed out of it.

The hardware that activates the BSL during reset

may be a simple pull-down resistor on P0L.4 for

systems

that

use

this

feature

upon

every

hardware reset.

A switchable solution (via jumper or an external

signal)

can

used

for

systems

that

only temporarily use the bootstrap loader (see

Figure 6).

After

sending

the

identification

Byte

the

ASC0 receiver

enabled

and

ready

receive the initial 32 Bytes from the host. A half

duplex connection is therefore sufficient to feed

the BSL.

5.6.2 - Memory Configuration After Reset

The configuration (and the accessibility) of the

ST10F269Z2Qx’s memory areas after reset in

Bootstrap-Loader mode differs from the standard

case. Pin EA is not evaluated when BSL mode is

selected, and accesses to the internal Flash area

are partly redirected, while the ST10F269Z2Qx is

in BSL mode (see Figure 7). All code fetches are

made from the special Boot-ROM, while data

accesses read from the internal user Flash. Data

accesses

will

return

undefined

values

ROMless devices.

The code in the Boot-ROM is not an invariant

feature of the ST10F269Z2Qx. User software

should not try to execute code from the internal

Flash area while the BSL mode is still active, as

these fetches will be redirected to the Boot-ROM.

The Boot-ROM will also “move” to segment 1,

when the internal Flash area is mapped to

segment 1 (see Figure 7).

Watchdog Timer:

Disabled

0E00h

Context Pointer CP:

FA00h

FA40h

Stack Pointer SP:

FA40h

FA0Ch 0<->C

8011h

acc. to startup configuration

Acc. to ‘00’ Byte

P3.10 / TXD0:

‘1’

DP3.10:

‘1’

Figure 6 : Hardware Provisions to Activate the BSL

RPOL.4

Ω

Circuit 1

POL.4

Normal Boot

BSL

External

Signal

RPOL.4

Ω

Circuit 2

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