ICS90C65

The Integrated Circuit Systems Video Graphics Array Clock Generator (ICS90C65) is capable of producing different output frequencies under firmware control. The video output frequency is derived from a 14.318 MHz system clock available in IBM PC/XT/AT and Personal System/2 computers. It is designed to work with Western Digital Imaging Video Graphics Array and 8514/A devices to optimize video subsystem performance.

The video dot clock output may be one of 15 internallygenerated frequencies or one external input. The selection of the video dot clock frequency is done through four inputs.
· VSEL0
· VSEL1
· VSEL2
· VSEL3

VSEL0 and VSEL1 of the ICS90C65 are latched by the SELEN signal. VSEL2 and VSEL3 are used as direct inputs to the VCLK selection. Table 1-1 is the truth table for VCLK selection.

The input and truth table have been designed to allow a direct connection to one of the many Western Digital Imaging VGA controllers or 8514/A chip sets.

The MCLK output is one of eight internally-generated frequencies as shown in Table 1-2. The various VCLK and MCLK frequencies are derived from the 14.318 MHz input frequency.

The VCLKE and MCLKE input of the ICS90C65 can tristate the VCLK and MCLK outputs to facilitate board level testing.