BT458

m o .c U 4 t e Bt457/Bt458 e h S MHz/165 MHz Monolithic CMOS 256 Color Palette 125 MHz/135 a RAMDAC at .D Distinguishing Features w w w The Bt457 and Bt458 are pin- and software-compatible RAMDACs designed specifically for high-performance, high-resolution color graphics. The architecture enables a display of 1280 x 1024 bit-mapped color graphics (up to 8 bits per pixel plus up to 2 bits of overlay information). This minimizes the use of costly ECL interfacing, because most of the high-speed (pixel clock) logic is contained on-chip. The multiple pixel ports and internal multiplexing enable TTL-compatible interface (up to 32 MHz) to the frame buffer, while maintaining the 165 MHz video data rates required for sophisticated color graphics. The Bt457 is a single-channel version of the Bt458 and has a 256 x 8 color lookup table with a single 8-bit video D/A converter. It includes a PLL output to enable subpixel synchronization of multiple Bt457s. On-chip features include programmable blink rates, bit plane masking and blinking, color overlay capability, and a dual-port color palette RAM. Functional Block Diagram CLOCK* LD* P[7:0] 40 (A-E) Latch OL[1,0] 10 (A-E) SYNC* BLANK* m o .c U 4 t e e h S a t a .D w w w 165, 135, 125, 110, 80 MHz operation 4:1 or 5:1 input mux 256-word dual-port color palette Four dual-port overlay registers RS-343A-compatible outputs Bit plane read and blink masks Standard MPU interface 84-pin PLCC or PGA package +5 V CMOS monolit...