Understanding data sheets.

The UD$61464$ is a $64kx4$ bit dynamic ram. The datasheet for this chip can be found at the Canvas site, in the homework directory, labeled $"$UD$61464-$datasheet.pdf$".64$k corresponds to a $16$ bit address space, but locations are arranged in $256$ rows of $256$ columns each. Sequential memory locations start at row $0,$ column $0$ and proceed by column, after column $255,$ they advance to column $1,$ and so on$.$ In other words, for a $16$ bit address, the most signifcant $8$ bits are the column and the least significant $8$ bits are the row; that is$,$ in hex, the address is decodes at $0$xRRCC$.$ So for example, $($decimal$)$ address $13576$ is $($google it$)0$x$3508$ or row $=0$x$35(53$ decimal$),$ column $8(8$ decimal$).$

Like most memory chips, the UD$61464$ uses the same $8$ address lines for the row and column numbers, and what they're interpreted as depends on the $\frac{?}{\text{b}\text{a}\text{r}}(RAS)$ and $\frac{?}{\text{b}\text{a}\text{r}}(CAS)$ lines. In "Fast Page Mode Write", the key signals are act as follows:

$\frac{?}{\text{b}\text{a}\text{r}}(RAS)-$ When this signal goes from HI to LO$,$ the chip will latch $8$ address bits $A[7$:$0]$ in as the ROW number, and hold them for as long as the bit remains LO$.$

$\frac{?}{\text{b}\text{a}\text{r}}(CAS)-$ When this signal goes from HI to LO$,$ the chip will load the $8$ address bit $A[7$:$0]$ as the COLUMN number. If the $\frac{?}{\text{b}\text{a}\text{r}}(W)$ bit is also LO at this time, it will write the data on bits $D[3$:$0]$ into the memory location corresponding to the current ROW and COLUMN.