Electrical computers and digital processing systems: processing – Processing control – Processing control for data transfer
Reexamination Certificate
1998-12-17
2001-01-30
Ellis, Richard L. (Department: 2783)
Electrical computers and digital processing systems: processing
Processing control
Processing control for data transfer
C712S036000, C712S038000, C711S103000, C711S219000
Reexamination Certificate
active
06182207
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to microcontrollers, and, more particularly, to a microcontroller interface.
DESCRIPTION OF THE PRIOR ART
A microcontroller is a circuit that includes a microprocessor or a central processing unit, and a program memory on the same integrated circuit. A set of instructions for the microprocessor is stored in the program memory, and is adapted to a program or application executable by the microcontroller. There are known microcontrollers with sets of instructions that are powerful in varying degrees. These programs vary in size depending on the application for which they are intended. Example applications include control of a hard disk in a compatible type microcomputer, or control of an element, such as flasher lights in an automobile.
Conceiving and finalizing a set of instructions for the microcontroller program is often a slow and tedious process. The microcontroller has an interface to exchange information external to the microcontroller. This information includes data to be received and data to be sent, which corresponds to the intended use of the microcontroller. To support this exchange of information, the interface has a control bus and, more generally, two data exchange registers or address exchange registers.
The interface is generally a wired circuit that provides for a series-parallel conversion between a protocol (parallel) internal to the microcontroller, and a protocol (series) generally used to interface the microcontroller. More generally, the interface has protocol conversion circuits. In certain cases, the control bus itself is non-existent. The control bus is replaced by a particular configuration of bits of words loaded into the exchange registers.
For cost reasons, it is acceptable to reduce the exchange structure external to the microcontroller to a strict minimum. In particular, this is why the number of registers are small. As a result, the use of the microcontroller becomes cumbersome, especially during a phase of setting the control program. During the setting phase, the microcontroller is connected to a host circuit. The purpose of this connection is to monitor the operation of the microcontroller. In this case, it is necessary to read electrical states of the microcontroller at certain stages, e.g., those stages where a faulty operation has been detected.
Another purpose of the connection is to set the operation of the microcontroller. In this case, the host circuit writes states in certain registers of the microcontroller. For each read action performed on the microcontroller, the host circuit has to initiate three operations. The first operation includes loading into the exchange registers a read command and the address where data must be read in the microcontroller. The second operation relates to the execution of the command that has been loaded. The third operation relates to reading in an exchange register of the data element read at the indicated address.
This mechanism is lengthy. A problem of the duration of the finalizing process arises, especially when the number of locations of the microcontroller memory to be read is large. At the time of the write operation for the setting of the microcontroller, the operation is slightly shorter. A first step includes loading of the write command and the data to be read, as well as the address at which the data must be written in the memory (or in a register) of the microcontroller. In a second step, the host circuit commands the microcontroller to carry out the write instruction available in the exchange registers. In the above described case, two steps are needed to modify a data element which is too lengthy.
Memory locations in the memory of the microcontroller where writing or reading is to be performed are varied. Hereinafter, this description limits itself to the term “memory.” The term “memory of the microcontroller” relates to the memory and the working registers of the microcontroller. This memory may thus be a program memory, i.e., where the instructions to be performed are stored in the microprocessor. This memory may also be a data memory, i.e., where the measured data or control parameters of the microcontroller are stored.
Finally, this memory could represent a batch of parameter-setting registers or operation registers of the microcontroller. In particular, the memory represents a batch of registers for setting the parameters of its peripherals. Because the interface itself is likely to accept different protocols, the interface must have its parameters set by states stored in the registers. Other peripherals such as internal counters, clock frequency registers, or even registers for monitoring the microcontroller are thus effected by the exchanges with the interface.
In particular, with regard to monitoring of the operation of the microcontroller, certain applications set up supplementary registers that can be used, in emulation, to monitor the operation of the microcontroller. This monitoring is necessary during the finalizing steps. Thus, the slowness of the communications carried out at the interface is further emphasized by the structurally complicated relationship with the supplementary registers in an indirect addressing mode.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a microcontroller with an improved interface, as well as a method for using the microcontroller with its improved interface. The present invention seeks to accelerate the interface between a microcontroller and devices external to the microcontroller. This acceleration primarily relates to the final adjusting of the operation of the microcontroller. However, it could relate to any conventional phase of use of the microcontroller.
It is an object of the invention to resolve the slowness of the exchanges by accelerating operations of the interface. Rather than follow a three-step operation or a two-step operation for the write operation, the invention modifies the architecture of the microcontroller so that it can be performed in only one step. In the invention, the interface is provided with an auxiliary supplementary register. Furthermore, there is a provision for automatically incrementing the address contained in one of the two exchange registers initially provided. For the finalizing process, it is primarily the monitoring of the registers or of the contiguous address memory locations that is performed. Consequently, an incrementation circuit added to the structure of the invention automatically provides an address increment. In practice, the address increment is equal to 1, but could nevertheless be arranged differently.
In one approach, the incrementation circuit is correlated to the reading or writing of the auxiliary register. Thus, it is sufficient to read or write the auxiliary register so that a command loaded into the control register is automatically executed. It can also be shown that management of the interfaces is carried out three times faster.
Another object of the invention therefore is to provide a microcontroller that includes a central processing unit, a program and/or data memory connected with the central processing unit, an input/output interface, a first exchange register containing an instruction code and an information element pertaining to a data element to be read or written, and a second exchange register containing an address. The first and second registers are connected to the interface. A switching circuit is connected to the interface, the program memory, and the central processing unit to carry out the switch-over as a function of a control signal. The control signal is available at this interface to provide a connection between the central processing unit and the program memory to provide a connection between the two exchange registers and the central processing unit.
The microcontroller also includes an auxiliary register connected to the interface, an automatic address implementation circuit to increment the value of an address contained in the second exchange register, and means for indirect addressing
Bosset Jean-Hugues
Poivre Gregory
Allen, Dyer, Doppelt, Milbrath & Gilchrist, P.A
Ellis Richard L.
Galanthay Theodore E.
STMicroelectronics S.A.
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