HD74HC670

HD74HC670 4-by-4 Register File (with 3-state outputs) Description The HD74HC670, 16-bit register file is organized as 4 words of 4 bits each and separate on-chip decoding is provided for addressing the four word locations to either write-in or retrieve data. This permits simultaneous writing into one location and reading from another word location. Four data inputs are available which are used to supply the 4-bit word to be stored. Location of the word is determined by the write-address inputs A and B in conjunction with a write-enable signal. Data applied at the inputs should be in its true form. That is, if a high-level signal is desired from the output, a high-level is applied at the data input for that particular bit location. The latch inputs are arranged so that new data will be accepted only if both internal address gate inputs are high. When this condition exists, data at the D input is transferred to the latch output. When the write-enable input, (G W ) is high, the data inputs are inhibited and their levels can cuase no change in the information stored in the internal latches. When the read-enable input, (GR) is high, the data outputs are inhibited and go into the high-impedance state. The individual address lines permit direct acquisition of data stored in any four of the latches. Four individual decoding gates are used to complete the address for reading a word. when the read address is made in conjunction with the read-enable signal, the word appears at the four...