Block access

The memory contained in a RAM-DISK is broken into blocks of 256 words. The CPU addresses the RAM-DISK in terms of blocks rather than words, so, with 12 bits address, the CPU can access up to (2^12 * 256) = 1 Mwords.

Before reading or writing to RAM-DISK, the CPU may do a write operation on the CONTROL register to specify the starting block. Once the block is defined, consecutive read or write operations on the DATA register will access consecutive words from that address up, meaning that blocks count is auto-incremented with each read or write cycle. Count will roll-over from FFFFF to 0.