SWITCHING DEVICE FOR DATA BUS WIDTH

摘要

PURPOSE:To simplify the interface with a CPU by switching between 8-bit and 16-bit bus widths according to '1' or '0' of a data bus width switching signal outputted to a signal line. CONSTITUTION:The 16-bit data bus width is selected when a CPU 2 generates '0' as a bit width signal. Then the 16-bit data is transferred between a VRAM 7 and a video display controller 1. While the 8-bit data bus width is selected when the CPU 2 generates '1' as the bit width signal. Then the 16-bit data is divided into the low-order and high-order bytes and then transferred. In this case, the low-order or high-order byte of the transferred data is decided based on the contents of a specific bit of an address signal. In such constitution, the interface with the CPU 2 is simplified.