JPH0335324A - Microcomputer - Google Patents

Abstract

PURPOSE:To reduce the overhead produced when a subroutine is called and to attain the effective use of a register set by using a means to set partly the adjacent register sets with overlap for a register bank consisting of an internal RAM. CONSTITUTION:When a register number is designated in an instruction, this register number is added to the contents of a register pointer. Then an area (register) of an internal RAM pointed by the result of this addition is accessed. For instance, a parameter is set to a register 7 from a register 0 in a main routine and a subroutine is called out. Then '8' is subtracted from the contents of a register pointer at the side of the subroutine. As a result, the register 0 is mapped to the register 7 in the main routine and a register 8 is mapped to a register 15 in the subroutine respectively. Thus the parameter can be transferred with no transfer of data. Furthermore, the contents of the register pointer can be reduced by an amount equal to the number of registers necessary for the subroutine. Then the internal RAM is effectively used.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a microcomputer equipped with completely new register set setting means in a register bank.

<Prior art/problems to be solved by the invention> In conventional microcomputers, each register set in a register bank is independent, so when a subroutine is called, separate registers are used for the main routine and subroutine. When using sets, it becomes necessary to perform data transfer processing for passing parameters between register sectors, which increases overhead such as an increase in the number of instructions and an increase in processing time. Furthermore, since the number of registers in each register set is fixed, even subroutines and interrupt processing routines that do not use registers often occupy one register set.

The present invention has been made in order to improve the above-mentioned prior art, and aims at reducing the overhead when calling a subroutine and efficiently using register sets.

Means for Solving the Problems> The microcomputer of the present invention is provided with a means for setting a part of adjacent register sets in an overlapping manner in a register bank constituted by an internal RAM. This is a characteristic feature.

Function: By overlapping a part of the register set, data transfer processing for receiving and passing parameters, which was necessary in the past, can be made unnecessary. In addition, by appropriately setting the number of registers in the operating knob section according to the number of registers used in the subroutine, internal R
It becomes possible to use AM efficiently.

<Embodiment> An embodiment of a microcomputer according to the present invention will be described in detail below with reference to one drawing.

FIG. 1 shows an internal block diagram of an embodiment of a microcomputer according to the present invention. In the figure, DB is a data bus and ROM is a program memory.

The PC is a program counter, and the ALU is an arithmetic unit.

To, T□ are temporary registers, IR is an instruction register, ID is an instruction decoder, TC is a timing control unit, RA
M is the internal RAM, RP is a register pointer that specifies the position of one register on the internal RAM, and ADDER is an adder that adds the register number in the instruction register 15 and the contents of the register RP. This is the RAM address input. That is, when a register number is specified in an instruction, the register number and the contents of the register pointer are added, and the area (register) on the internal RAM indicated by the result is accessed.

For example, the number of registers that make up the register set is r16.
J (register 15 setting means register 15).

If the contents of the register pointer are rlooJ, then the internal R
A register is constructed from addresses 100 to 115 of AM, and when register 8 is specified, address 1 (M1) is accessed (see FIG. 2).

Register from register 0 (address 100) in the main routine? Set the parameters to (address 107) and call the subroutine. Next, on the subroutine side, by executing the process of subtracting "8" from the contents of the register pointer, registers 0 to 7 of the 2nd main routine are manoped to registers 8 to 15 of the subroutine, and the data is transferred as before. Parameters can be received and passed without any processing (see Figure 3).

Furthermore, the contents of the register pointer need only be reduced by the number of registers required for the subroutine, and the internal RAM can be used efficiently. For example, if the number of registers required for a subroutine is "5", then "5" can be subtracted.

<Effects of the Invention> As described above in detail, according to the present invention, parameters can be passed at high speed when a subroutine is called, and overhead can be reduced. It was a cabinet. Since the amount of internal RAM constituting a register bank can be set according to the number of registers used in the subroutine, the internal RAM can be used efficiently.

[Brief explanation of drawings]

FIG. 1 is an internal block diagram of an embodiment of a microcomputer according to the present invention, and FIG. 2 is a diagram showing the relationship between the contents of a register pointer and a register set. FIG. 8 is a diagram showing the relationship between the main routine register set and the subroutine register set. Code explanation RAM: Internal RAM, RP register pointer, AD
DER: Adder.

Claims (1)

[Claims] 1. A microcomputer characterized by comprising means for setting a part of adjacent register sets in an overlapping manner in a register bank constituted by an internal RAM.