16-Deep by 4-Wide Static RAM

The digital RAM is an 4-wide, 16-deep random access memory element with programmable select lines, tristated data_out lines, and a single write/read line.

There is no reset line into the device. However, an initial value for all bits may be specified by setting the ic parameter to either 0 or 1. In reading a word from the ram, the read_delay value is invoked, and output will not appear until that delay has been satisfied. Separate rise and fall delays are not supported for this device.

Note that UNKNOWN inputs on the address lines are not allowed during a write. In the event that an address line does indeed go unknown during a write, THE ENTIRE CONTENTS OF THE RAM WILL BE SET TO UNKNOWN. This is in contrast to the data_in lines being set to unknown during a write; in that case, only the selected word will be corrupted, and this is corrected once the data lines settle back to a known value. Note that protection is added to the write_en line such that extended UNKNOWN values on that line are interpreted as ZERO values. This is the equivalent of a read operation and will not corrupt the contents of the RAM. A similar mechanism exists for the select lines. If they are unknown, then it is assumed that the chip is not selected.

Parameters