The SMJ44C251B multiport video RAM is a high-speed, dual-ported memory device. It consists of a dynamic random-access memory (DRAM) organized as 262 144 words of 4 bits each interfaced to a serial-data register or serial-access memory (SAM) organized as 512 words of 4 bits each. The SMJ44C251B supports three types of operation: random access to and from the DRAM, serial access to and from the serial register, and bidirectional transfer of data between any row in the DRAM and the serial register. Except during transfer operations, the SMJ44C251B can be accessed simultaneously and asynchronously from the DRAM and SAM ports.