RAM data transmitting apparatus and method using a FIFO memory with three fullness flags

An apparatus for transmitting data from a random access memory (RAM) comprising:

• a first-in first-out (FIFO) memory having a storage capacity, for sequentially receiving RAM data from the RAM in response to a write enable signal, wherein the FIFO memory has a first flag, a second flag, and a third flag as outputs, said first flag being generated when RAM data from the RAM is written to a first portion of the FIFO memory, said first portion being smaller than said storage capacity of the FIFO memory, said second flag being generated when the RAM data is written so as to fill a second portion of the FIFO memory, said second portion being smaller than said storage capacity of the FIFO memory and larger than said first portion, said third flag being generated when no RAM data is contained in the FIFO memory;
• RAM data transmission request signal generating means for generating a RAM data transmission request signal when said first flag is generated and until a time when said second flag is generated, and if said second flag is generated, blocking said RAM data transmission request signal until a first flag is again generated;
• RAM controlling means for selecting RAM data to be written in the FIFO memory among the RAM data stored in the RAM in response to the generation of said RAM data transmission request signal and generating said write enable signal after the selection of the RAM data so as to write selected RAM data in said FIFO memory;
• and
• data access means for continuously accessing the RAM data written in the FIFO memory,
• wherein a size of said first portion is adjustable by setting a setting value of said RAM controlling means, so that the generation of said first flag and said second flag are adjustable depending on the size of said first portion, and said adjustable generation of said first flag allows said data access means to continuously access the RAM data in the FIFO memory after said second flag is generated, and during a period of time until subsequently said third flag is generated, said period of time changing depending on said adjustable generation of said first flag and said second flag.

A method of writing RAM data stored in a RAM into a first-in first-out memory having a storage capacity and if there is a request of an access from data access means, transmitting the RAM data written in said first-in first-out memory to said data access means, said method comprising the steps of:

• generating a first flag when the RAM data is written in a first area of the first-in first-out memory;
• generating a second flag when the RAM data is written so as to fill a second area of the first-in first-out memory, said second area being larger than said first area and smaller than said storage capacity;
• generating a third flag when no RAM data is written in the first-in first-out memory;
• writing the RAM data stored in said RAM into the first-in first-out memory when said first flag is generated and until said second flag is generated;
• accessing the RAM data written in said first-in first-out memory to said data access means, when said second flag is generated and in response to an access request of said data access means;
• and
• halting the accessing step when said third flag is generated, and
• adjusting a size of said first area so that the generation of said first flag and said second flag is adjustable depending on the size of said first area, and said adjustable generation of said first flag allows said data access means to continuously access the data in the first-in-first-out memory in said accessing step from a period of time after said second flag is generated until said third flag is generated and said halting step is conducted, said period of time changing depending on said adjusting step and said adjustable generation of said first flag and said second flag.