The MC141541 is a high performance HCMOS device designed to interface with a microcontroller unit to allow colored symbols or characters to be displayed on a color monitor. The onchip PLL allows both multisystem operation and selfgeneration of system timing. It also minimizes the MCU's burden through its builtin 273 bytes display/control RAM. By storing a full screen of data and control information, this device has the capability to carry out `screenrefresh' without MCU supervision. Since there is no spacing between characters, special graphicsoriented characters can be generated by combining two or more character blocks. There are two different resolutions that users can choose. By changing the number of dots per horizontal line to 320 (CGA) or 480 (EGA), smaller characters with higher resolution can be easily achieved. Special functions such as character bordering or shadowing, multilevel windows, double height and double width, and programmable vertical length of character can also be incorporated. Furthermore, neither massive information update nor extremely high data transmission rate are expected for normal on screen display operation, and serial protocols are implemented in lieu of any parallel formats to achieve minimum pin count. A special feature, character RAM fonts, is implemented in this MOSD enhanced version (EMOSD). Users can download their own fonts and display them at any time once the chip is powered on. There are two ways for users to build and store fonts. One is a conventional approach to have masked ROM fonts. A newer approach is to store the fonts in the EPROM accessed by the MCU and then download them into the EMOSD character RAM. With this new technique, users have more flexibility in preparing their fonts and the effective number of fonts is greatly increased.