Video memory interface circuit

Claim 2

A video display circuit operable for receiving and storing character code data provided by a processor and for supplying character pixel data to a video display device, wherein the character code data specifies which characters are to be visually displayed and the character pixel data defines the pixel representations of the characters, said circuit comprising: a controller chip for receiving the character code data from the processor, and for supplying the character pixel data to the video display device; and memory means coupled to said controller chip and operable for storing the character code data of the characters to be displayed in a character memory of said memory means and for storing the character pixel data of all of the characters in a character set in a font memory of said memory means, said character memory including address and data pins connected to said controller chip and being operable for storing the character code data received from the processor, said font memory being operable for storing in a block of memory cells the character pixel data for each character of the character set, said font memory including character font address pins that select a block of memory cells corresponding to a character whose character code is applied to said character font address pins and including row address pins that select a row of memory cells within said block of memory cells, and wherein data pins and said row address pins of said font memory are connected to said controller chip and said character font address pins of said font memory and said data pins of said character memory are connected in common to said controller chip.

Claim 3

A circuit as recited in claim 1 further comprising an attribute memory having address and data pins connected to said controller chip and operable for storing attribute data received from the processor, where the attribute data identifies attributes of characters stored in said character memory at corresponding addresses, wherein said address pins of said attribute memory and said address pins of said character memory are connected in common to said controller chip.

Claim 4

A circuit as recited in claim 2 wherein one or more of said data pins of said font memory are connected to said controller chip in common with one or more of said data pins of said attribute memory, and wherein said controller chip further includes enable means for alternatively supplying attribute data to or receiving attribute data from said attribute memory and receiving character pixel data from said font memory.

Claim 5

A circuit as recited in claim 1 operable in a character mode for receiving and storing character code data provided by the processor and for supplying character pixel data to the video display device, and operable in a graphics mode for receiving graphics display data provided by the processor, storing the graphics display data in said character and font memories, and supplying the graphics display data to the video display device, wherein said circuit further comprises an extra memory connected to said controller chip through data pins and address pins, and wherein said address pins of said extra memory and said address pins of said font memory are connected in common to said controller chip, said extra memory being operable for storing a portion of the graphics display data provided by the processor and for supplying that graphics display data to said controller chip in parallel with the graphics display data stored in said font memory.

Claim 6

A circuit as recited in claim 4 further comprising an attribute memory having data pins connected to said controller chip and having address pins connected in common with said address pins of said character memory to said controller chip, said attribute memory stores attribute data that identifies attributes of characters stored in said character memory at corresponding addresses when said circuit operates in said character mode, and said attribute memory stores the graphics display data provided by the processor and supplies the graphics display data to said controller chip in parallel with the graphics display data stored in said character memory when said circuit operates in said graphics mode.

Claim 7

A circuit as recited in claim 5 wherein one or more of said data pins of said extra memory are connected to said controller chip in common with one or more of said address pins of said attribute and character memories, wherein one or more of said data pins of said font memory are connected to said controller chip in common with one or more of said data pins of said attribute memory, and wherein said controller chip further includes enable means for alternatively supplying address data to said address pins of said attribute and character memories and receiving graphics display data from said extra memory, and includes enable means for alternatively supplying data to or receiving data from said data pins of said attribute memory and receiving character pixel data or graphics display data from said font memory.

Claim 8

A circuit as recited in claim 1 wherein said font memory further includes a font select address pin connected to said controller chip for selecting alternative blocks of memory cells containing alternative character pixel data for the characters of the character set.

Claim 9

A circuit as recited in claim 1 wherein said row address pins of said font memory are connected in common with signal lines coupled to the video display device, and wherein said controller chip includes multiplexing means for alternatively supplying row addresses to said font memory and supplying data to the video display device through said signal lines.

Claim 10

A video display circuit operable in a character mode for receiving and storing character code data and attribute data provided by a processor and for supplying corresponding character pixel data to a video display device, and operable in a graphics mode for receiving and storing graphics display data provided by the processor and for supplying the graphics display data to the video display device, wherein the character code data identifies characters to be displayed, the attribute data identifies attributes of the characters to be displayed, the character pixel data specifies pixel representations of the characters to be displayed, and the graphics display data specifies pixel representations of graphics information to be displayed, said circuit comprising: a controller chip for receiving the character code data and the graphics display data from the processor, and for supplying the character pixel data and the graphics display data to the video display device; and memory means coupled to said controller chip and operable in the character mode for storing the character code data of the characters to be displayed and the character pixel data of all of the characters in a character set, and operable in graphics mode for storing the graphics display data; wherein said memory means includes a character memory chip, an attribute memory chip, a font memory chip, and an extra memory chip; said character memory chip including address and data pins connected to said controller chip, said character memory chip operable in character mode for storing the character code data and operable in graphics mode for storing a portion of the graphics display data; said attribute memory chip including data pins connected to said controller chip and address pins connected in common with said address pins of said character memory chip to said controller chip, said attribute memory chip operable in character mode for storing attribute data of characters stored in said character memory chip at corresponding addresses, and operable in graphics mode for storing a portion of the graphics display data and supplying the graphics display data to said controller chip in parallel with said character memory chip; said font memory chip including data pins connected to said controller chip in common with said data pins of said attribute memory chip, including row address pins connected to said controller chip, and including character font address pins connected to said controller chip in common with said data pins of said character memory chip, said font memory chip being operable in character mode for storing in blocks of memory cells the character pixel data for the characters of the character set and operable in graphics mode for storing a portion of the graphics display data, wherein in character mode said character memory chip applies character code data to said character font address pins to select a block of memory cells corresponding to a character code stored in said character memory chip, and wherein said row address pins select a row of memory cells within said block of memory cells; said extra memory chip including address pins connected to said controller chip in common with said address pins of said font memory chip and data pins connected to said controller chip in common with one or more of said address pins of said attribute and character memory chips, said extra memory chip being operable in graphics mode for storing a portion of the graphics display data and for supplying the graphics display data to said controller chip in parallel with said font memory chip; and wherein said controller chip further includes enable means for alternatively supplying data to or receiving data from said data pins of said attribute memory ship and supplying data to and receiving data from said data pins of said font memory chip, and includes enable means for alternatively supplying address data to said address pins of said attribute and character memory chips and receiving graphics display data from said extra memory chip.

Claim 11

A video display circuit operable in a character mode for receiving and storing character code data and attribute data provided by a processor and for supplying corresponding character pixel data to a video display device, and operable in a graphics mode for receiving and storing graphics display data provided by the processor and for supplying the graphics display data to the video display device, wherein the character code data identifies characters to be displayed, the attribute data identifies attributes of the characters to be displayed, the character pixel data specifies pixel representations of the characters to be displayed, and the graphics display data specifies pixel representations of graphics information to be displayed, said circuit comprising: a controller chip for receiving the character code data and the graphics display data from the processor, and for supplying the character pixel data and the graphics display data to the video display device; and memory means coupled to said controller chip and operable in the character mode for storing the character code data of the characters to be displayed and the character pixel data of all of the characters in a character set, and operable in graphics mode for storing the graphics display data; wherein said memory means includes a character memory chip, an attribute memory chip, a font memory chip, and an extra memory chip; said character memory chip including address and data pins connected to said controller chip, said character memory chip operable in character mode for storing the character code data and operable in graphics mode for storing a portion of the graphics display data; said attribute memory chip including data pins connected to said controller chip and address pins connected in common with said address pins of said character memory chip to said controller chip, said attribute memory chip operable in character mode for storing attribute data of characters stored in said character memory chip at corresponding addresses, and operable in graphics mode for storing a portion of the graphics display data and supplying the graphics display data to said controller chip in parallel with said character memory chip; said font memory chip including data pins connected to said controller chip in common with said data pins of said attribute memory chip, including row address pins connected to said controller chip, and including character font address pins connected to said controller chip in common with said data pins of said character memory chip, said font memory chip being operable in character mode for storing in blocks of memory cells the character pixel data for the characters of the character set and operable in graphics mode for storing a portion of the graphics display data, wherein in character mode said character memory chip applies character code data to said character font address pins to select a block of memory cells corresponding to a character code stored in said character memory chip, and wherein said row address pins select a row of memory cells within said block of memory cells; said extra memory chip including address pins connected to said controller chip in common with said address pins of said font memory chip and data pins connected to said controller chip in common with one or more of said address pins of said attribute and character memory chips, said extra memory chip being operable in graphics mode for storing a portion of the graphics display data and for supplying the graphics display data to said controller chip in parallel with said font memory chip; and wherein said controller chip further includes enable means for alternatively supplying data to or receiving data from said data pins of said attribute memory ship and supplying data to and receiving data from said data pins of said font memory chip, and includes enable means for alternatively supplying address data to said address pins of said attribute and character memory chips and receiving graphics display data from said extra memory chip.

Claim 14

A method for receiving and storing character code data and attribute data provided by a processor and for supplying character pixel data to a video display device, as recited in claim 10, wherein the attribute data identifies attributes of characters stored at corresponding addresses in said character memory, said method further comprising the step of receiving the attribute data from the processor by said controller chip and storing the attribute data in an attribute memory, said attribute memory having address pins connected to said controller chip in common with address pins of said character memory, wherein said step of addressing a memory location in said character memory includes simultaneously addressing a corresponding memory location in said attribute memory, and wherein said step of supplying the character code data includes simultaneously supplying corresponding attribute data to said controller chip.

Claim 15

A method as recited in claim 11 wherein one or more data pins of said font memory are connected to said controller chip in common with one or more data pins of said attribute memory, wherein said step of receiving the attribute data from said controller chip includes supplying a write enable signal to said attribute memory, and wherein said step of supplying character pixel data to said controller chip includes supplying an output enable signal to said font memory.

Claim 16

A method for receiving and storing character code data provided by the processor and for supplying character pixel data to the video display device during operation in a character mode, as recited in claim 10, further comprising the steps of receiving graphics display data provided by the processor, storing the graphics display data in said character and font memories and in an extra memory, and supplying the graphics display data to the video display device during operation in a graphics mode, wherein said extra memory includes data pins connected to said controller chip and includes address pins connected to said controller chip in common with said address pins of said font memory, said extra memory being operable for storing a portion of the graphics display data and for supplying the graphics display data to said controller chip in parallel with said font memory.

Claim 17

A method for receiving and storing character code data and attribute data provided by a processor and for supplying character pixel data to a video display device during operation in character mode, as recited in claim 13, wherein the attribute data identifies attributes of characters stored at corresponding addresses in said character memory, said method further comprising the step of receiving the attribute data from the processor by said controller chip and storing the attribute data in an attribute memory during operation in character mode, said attribute memory having address pins connected to said controller chip in common with address pins of said character memory, wherein during operation in character mode said step of addressing a memory location in said character memory includes simultaneously addressing a corresponding memory location in said attribute memory and said step of supplying the character code data includes simultaneously supplying corresponding attribute data to said controller chip, and wherein during operation in graphics mode said step of storing the graphics display data includes storing a portion of the graphics display data in said attribute memory and said step of supplying the graphics data includes supplying graphics display data from said attribute memory to said controller chip in parallel with graphics display data from said character memory.

Claim 18

A method as recited in claim 10 wherein said step of supplying character pixel data further includes the step of supplying a font select signal to a font select address pin of said font memory for selecting alternative blocks of memory cells containing alternative character pixel data for the characters of the character set.