ST10F276 datasheet(68/229 Pages) STMICROELECTRONICS

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Bootstrap loader

ST10F276

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5.6.11

Internal decoding of test modes

The test mode decoding logic is located inside the ST10F276 Bus Controller.

The decoding is as follows:

●

Alternate Boot Mode decoding: (P0L.5 & P0L.4)

●

Standard Bootstrap decoding: (P0L.5 & P0L.4)

●

Normal operation: (P0L.5 & P0L.4)

The other configurations select ST internal test modes.

5.6.12

Example

In the following example, Alternate Boot Mode works as follows:

–

On rising edge of RSTIN pin, the reset configuration is latched.

●

If Bootstrap Loader mode is not enabled (P0L[5..4] = ‘11’), ST10F276 hardware

proceeds with a standard hardware reset procedure.

●

If standard Bootstrap Loader is enabled (P0L[5..4] = ‘10’), the standard ST10 Bootstrap

Loader is enabled and a variable is cleared to indicate that ABM is not enabled.

●

If Alternate Boot Mode is selected (P0L[5..4] = ‘01’), then, depending on signatures

integrity checks, a predefined reset sequence is activated.

5.7

Selective boot mode

The selective boot is a subcase of the Alternate Boot Mode. When none of the signatures

are correct, instead of executing the standard bootstrap loader (triggered by P0L.4 low at

reset), an additional check is made.

Address 00’1FFCh is read again with the following behavior:

●

If value is 0000h or FFFFh, a jump is performed to the standard bootstrap loader.

●

Otherwise:

–

High byte is disregarded.

–

Low byte bits select which communication channel is enabled.

Table 36.

ABM bit description

Bit

Function

ABM

ABM Flag (or TMOD3)

‘0’: Alternate Boot Mode is not selected by reset configuration on P0L[5..4]

‘1’: Alternate Boot Mode is selected by reset configuration on P0L[5..4]: This bit is

set if P0L[5..4] = ‘01’ during hardware reset.

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