Microcontroller having a memory, a dedicated multitask memory, and switching circuit for selectively connecting the multitask memory to the internal or external bus

• US 6,175,881 B1
• Filed: 03/12/1998
• Issued: 01/16/2001
• Est. Priority Date: 05/28/1997
• Status: Expired due to Fees

• Current Assignee: Oki Semiconductor Company Limited (ROHM Co., Ltd.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Tanagawa, Kouji
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): VUONG, THU HUONG T
• Application Number:
  US09/038,836
• Time in Patent Office: 1,041 Days
• Field of Search: 711/163, 711/150, 358/296, 370/351, 710/20, 710/7
• US Class Current: 710/7
• CPC Class Codes: G06F 15/7857 using interleaved memory addressing G06F12/0607

Abstract

A microcontroller comprising a first memory 2 used by a CPU1 to perform arithmetic operations; a second memory 3 for a multitask process for storing data transferred from an external device 30 during the arithmetic process of CPU1; bus switches 4 and 5 for switching over the connection of data buses of CPU1 and the external device 30; and an address supply portion 7, which is connected to the address bus of the external device 30 while the second memory 3 is connected to the data bus of the external device 30, and which generates address signals by which to store data from the external device, wherein this microcontroller can perform a multitask process without adopting an expensive device such as a dual port RAM.

Claims

1. A microcontroller having a memory connected to a CPU through a data bus and an address bus, comprising:

a memory for a multitask process separate from said memory;

data bus switching means for switching, by control of said CPU, the connection of said multitask-process memory either to said data bus or a data bus leading to an external device;

address bus switching means for switching, by control of said CPU, the connection of said multitask-process memory either to said address bus or to an address bus for said external device; and

address supply means for generating and supplying address signals used to store data sent from said external device in the multitask-process memory connected both to the data bus of said external device and said address bus data.

2. A microcontroller according to claim 1, wherein said address supply means is connected to a clock oscillator which oscillates at the same clock frequency as the clock frequency of said external device.