Liquid-crystal display control apparatus

• US 6,259,421 B1
• Filed: 08/05/1999
• Issued: 07/10/2001
• Est. Priority Date: 08/21/1992
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Hitachi Device Engineering Co., Ltd. (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Yokota, Yoshikazu, Sugiyama, Kimihiko, Tsunekawa, Satoru
• Primary Examiner(s): Mengistu, Amare
• Application Number:
  US09/369,121
• Time in Patent Office: 705 Days
• Field of Search: 345/1, 345/3, 345/33, 345/34, 345/50, 345/87, 345/98, 345/116, 345/141, 345/192-194, 345/199
• US Class Current: 345/33
• CPC Class Codes: G09G 3/18 using liquid crystals

Abstract

The liquid-crystal display control apparatus provided by the present invention includes a display RAM unit for storing character codes, character-generator RAM and ROM units for storing character font patterns, and a segment RAM unit for storing picture patterns such as marks and icons. When displaying a character, the following display control is carried out. First of all, a character code is read out from the display RAM unit at a display address generated by a display-address counter. The character code is then used in conjunction with a raster address output by a line-address counter for reading out a character font pattern from the character-generator RAM unit or the character-generator ROM unit. When displaying a picture pattern such as a mark or an icon, on the other hand, the following display control is carried out. Display control information is read out from the segment RAM unit at an address generated by the display-address counter. Dot-matrix characters and picture patterns such as marks and icons are displayed on the same screen on a time-division basis.

Claims

1. A liquid-crystal display system comprising:

a liquid-crystal display unit having;

first common lines;

a second common line; and

segment lines arranged to cross said first common lines and said second common line;

wherein first portions where the segment lines and the first common lines are overlapped have dots to be used for displaying character font patterns; and

wherein second portions where the segment lines and the second common line are overlapped have predetermined picture patterns; and

a liquid-crystal display controller formed on a semiconductor chip and including;

a common line driver circuit cyclically driving the first common lines and the second common line;

a first memory storing character codes to be displayed on the liquid-crystal display unit;

a character memory coupled to the first memory and storing character font pattern information corresponding to the character codes stored in the first memory, the character memory being responsive to reception of a predetermined character code from said first memory and outputting predetermined character font pattern information corresponding to the predetermined character code;

a second memory storing segment control information representing whether or not each of the predetermined picture patterns in the liquid-crystal display unit is displayed on the liquid-crystal display unit;

a segment line driver, coupled to the character memory and the second memory, driving the segment lines in accordance with one of the segment control information from the segment memory and character font information from the character memory; and

an address providing circuit providing a display address to said first memory in synchronism with the driving of said first common lines while said display address is provided to said second memory in synchronism with the driving of said second common line.

2. A liquid-crystal display system according to claim 1,

wherein the second memory further stores blinking information indicating whether or not the predetermined picture patterns to be displayed are to be blinking.

3. A liquid-crystal display system according to claim 1,

wherein the address providing circuit further includes a rewritable address providing circuit which provides a rewritable address indicating an address in the first memory and the second memory so as to rewrite one of the character codes stored in the first memory or the segment control information stored in the second memory.

4. A liquid-crystal display system according to claim 3,

wherein an address space of the first memory is different from that of the second memory.

5. A liquid-crystal display system according to claim 1,

wherein the segment driver circuit includes:

a parallel-series converter which is coupled to receive the character font pattern information from the character memory and the segment control information from the second memory, and which converts the character font pattern information and the segment control information into the serial information, and

a segment driver which is coupled to receive the serial information and which drives the segment lines in accordance with the serial information.

6. A liquid-crystal display system according to claim 1,

wherein the character memory includes a read-only memory and a rewritable memory.

7. A liquid-crystal display system according to claim 6,

wherein the segment driver circuit includes:

a parallel-serial converter which is coupled to receive the character font pattern information from the character memory and the segment control information from the second memory, and which converts the character font pattern information and the segment control information into serial information, and

a segment driver which is coupled to receive the serial information and which drives the segment lines in accordance with the serial information.

8. A liquid-crystal display system according to claim 7,

wherein the second memory further stores blinking information indicating whether or not the predetermined picture patterns to be displayed are to be blinking.

9. A liquid-crystal display system according to claim 8,

wherein the address providing circuit further includes a rewritable address providing circuit which provides a rewritable address indicating an address in the first memory, the second memory and the rewritable memory and so as to rewrite one of the character codes stored in the first memory, the segment control information stored in the second memory and the character font pattern information stored in the rewritable memory.

10. A liquid-crystal display system according to claim 9,

wherein an address space of the first memory is different from that of the second memory.

11. A liquid-crystal display system comprising:

a CPU;

a liquid-crystal display unit having a dot-matrix portion displaying character font patterns and a segment portion displaying predetermined picture patterns;

wherein the dot-matrix portion has segment lines and first common lines, the segment lines and the first common lines in the dot-matrix portion being arranged to cross each other to form dots for the character font patterns;

wherein the segment portion has the segment lines and at least one second common line, the segment lines and the second common line in the segment portion being arranged to cross each other, the predetermined picture patterns being allocated at portions where the segment lines and the second common line in the segment portion are crossed; and

a liquid-crystal display controller which derives the first common lines and the second common line cyclically, wherein the liquid-crystal display controller provides the segment lines with character font pattern information to be displayed on said dot-matrix portion and with control information indicating whether or not each of the predetermined picture patterns in the segment portion is displayed, the liquid-crystal display controller comprising;

a first memory which stores therein character codes written by the CPU;

a character memory which stores the character font pattern information, and which outputs the corresponding character font pattern information to the segment lines in response to an output of predetermined character codes from said first memory;

a second memory which stores therein the control information written by the CPU; and

an address output circuit which provides first display addresses and second display addresses, wherein the first display addresses are provided to the first memory so as to read from the first memory the character codes of the character font patterns to be displayed on the dot-matrix portion so that the character memory is responsive to the character codes and provides the character font pattern information corresponding to the received character codes to the segment lines, and wherein the second display addresses are provided to the second memory so as to read from the second memory the control information of the predetermined picture patterns to be displayed on the segment portion so that the second memory provides the control information to the segment lines;

wherein the first display addresses are supplied to the first memory at a time when the character font patterns are displayed on the dot-matrix portion; and

wherein the second display addresses are supplied to said second memory at a time when the predetermined picture patterns are displayed on said segment portion.

12. A liquid-crystal display system according to claim 11,

wherein the address output circuit further comprises a rewrite-address output circuit which generates a rewrite address indicating an address in the first memory or the second memory to change one of the character codes in the address of the first memory or one of the control information in the address of the second memory.

13. A liquid-crystal display system according to claim 12,

wherein an address space of the first memory is different from that of the second memory.

14. A liquid-crystal display system according to claim 13,

wherein a second memory further stores blinking information for indicating whether or not the predetermined picture patterns are to be displayed in a blinking mode.

15. A liquid-crystal display system according to claim 14,

wherein the liquid-crystal display controller has a terminal to receive a clock signal having a predetermined frequency, and

wherein a period when a displayed predetermined picture pattern is blinking is determined by the clock signal.

16. A liquid-crystal display system according to claim 15,

wherein the liquid-crystal display controller further comprises:

a control circuit providing a control signal in response to information, provided from the CPU, which indicates to change one of the character codes in the first memory and the control information in the second memory; and

a switch circuit coupled to the address outputting circuit and responsive to the control signal from the control circuit, and providing to one of said first memory and said second memory the rewrite address from the rewrite-address output circuit instead of the first and the second display addresses from the address output circuit when the information is provided from the CPU to the control circuit.

17. A liquid-crystal display system according to claim 11,

wherein the character memory includes a rewritable memory.

18. A liquid-crystal display system according to claim 17,

wherein the address output circuit further comprises a rewrite-address output circuit generating a rewrite address indicating an address in the first memory, the character memory and the second memory to change one of the character codes in the first memory, the character font pattern information in the character memory and the control information in the second memory.

19. A liquid-crystal display system according to claim 18,

wherein the first memory, the character memory and the second memory have mutually different address spaces.

20. A liquid-crystal display system according to claim 19,

wherein the character memory further includes a read only memory.