Stmicroelectronics S.a.

Stmicroelectronics International N.v.

Stmicroelectronics (Grenoble 2) Sas

Gregory Poivre

Jean-Hugues Bosset

Ankur Behl

Embodiments disclosed herein generally relate for efficiently retrieving boot code for a processor from serial NOR flash memory. When a boot code request is received, a request handler in data capture logic tags successive address read requests to indicate whether the requests indicate contiguous addresses in the NOR flash memory for the boot code. Different circuitry in the data capture logic operates on different mesochronous clock signals. One clock signal drives the capture of boot code from NOR flash, and the other controls synchronized tagging, storing, pre-fetching, and transmitting of the captured boot code data.

Tag-based implementations enabling high speed data capture and transparent pre-fetch from a NOR flash

The microcontroller accesses a battery of hidden registers used essentially in the field of emulation. The fact that there is a large number of hidden registers means that it is not possible to assign them an address by which they can be accessed directly. Since this battery of hidden registers has to be accessible by a host circuit and by a microprocessor, recourse is had to a method of indirect addressing by means of two peripheral control registers. A priority signal obliges the microprocessor to wait for the read and write resources to be released by the host circuit to perform these instructions.

Sharing of the indirect addressing of the registers of a peripheral dedicated to emulation

To accelerate read operations, or the operations that modify the operating parameters of a microcontroller, an interface is provided with three registers&mdash;an address register, an instruction and data register, and an auxiliary register. The instruction and data register supports the auxiliary register by indirect addressing. The address register is furthermore provided with an incrementation circuit mechanism for indirect incrementation. With the indirect addressing and the automatic incrementation, the number of external operations are reduced for continuous read or write operations.

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Grenoble, France

Gregory Poivre