C167CS datasheet(312/517 Pages) INFINEON

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C167CS

Derivatives

The Bootstrap Loader

User’s Manual

15-2

V2.0, 2000-07

15.1

Entering the Bootstrap Loader

The C167CS enters BSL mode triggered by external configuration during a hardware

reset:

• when pin P0L.4 is sampled low at the end of an external reset (EA = ‘0’)

• when pin RD is sampled low at the end of an internal reset (EA = ‘1’).

In this case the built-in bootstrap loader is activated independent of the selected bus

mode. The bootstrap loader code is stored in a special Boot-ROM, no part of the

standard mask ROM, OTP, or Flash memory area is required for this.

The hardware that activates the BSL during reset may be a simple pull-down resistor on

P0L.4 or RD for systems that use this feature upon every hardware reset. You may want

to use a switchable solution (via jumper or an external signal) for systems that only

temporarily use the bootstrap loader.

Figure 15-2

Hardware Provisions to Activate the BSL

The ASC0 receiver is only enabled after the identification byte has been transmitted. A

half duplex connection to the host is therefore sufficient to feed the BSL.

Note: The proper reset configuration for BSL mode requires more pins to be driven

besides P0L.4 or RD.

For an external reset (EA = ‘0’) bitfield SMOD must be configured as 1011B (see

section Section 20.4.1).

For an internal reset (EA = ‘1’) pin ALE must be driven to a defined level, e.g.

ALE = ‘0’ for the standard bootstrap loader (see section Section 20.4.2).

MCA04466

P0L.4

Ext.

Signal

Start

Boot

~2 k

Proposal for Internal Reset

(EA = '1')

P0L.4

Ext.

Signal

Start

Boot

~8 k

Proposal for Internal Reset

(EA = '0')

P0L.4

Ext.

Signal

Start

Boot

Proposal for Combined Circuitry

~2 k

~8 k

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