The HM538123B is a 1-Mbit multiport video RAM equipped with a 128-kword x 8-bit dynamic RAM and a 256-word x 8-bit SAM (serial access memory). Its RAM and SAM operate independently and asynchronously. It can transfer data between RAM and SAM. In addition, it has two modes to realize fast writing in RAM. Block write and flash write modes clear the data of 4-word x 8-bit and the data of one row (256-word x 8-bit) respectively in one cycle of RAM. And the HM538123B makes split transfer cycle possible by dividing SAM into two split buffers equipped with 128-word x 8-bit each. This cycle can transfer data to SAM which is not active, and enables a continuous serial access.