7489: 64-Bit (16 × 4) Memory

This package contains a memory arranged as sixteen different words of four bits each. It keeps its internal information as long as power is applied.

To place information in the memory, a 4-bit word is placed on the 1 In, 2 In, 3 In, and 4 In lines. This is the information to be stored. Next, a location in the memory is selected by using Select or Address lines A, B, C, D. These are binarily weighted A = 1, B = 2, C = 4, D = 8. The Write Enable line is then brought low to enter the data. Information that was in the four storage locations corresponding to the selected address is destroyed. The Write Enable line is left high unless new information is to be entered in the memory.

The Read Enable line is normally left in the low condition, and the complement of the selected word will appear as an output. Do not change addresses with Write Enable low.

If both Read Enable and Write Enable are held high, the output goes to an open-circuit condition. The memory may be expanded by connecting package outputs together, so long as all packages but one have their Write Enable and Read Enable outputs held high at any given time.

Pinout
Pin # Pin Assignment
1 Address A
2 Read Enable
3 Write Enable
4 Input 1
5 Output 1
6 Input 2
7 Output 2
8 Ground
9 Output 3
10 Input 3
11 Output 4
12 Input 4
13 Address D
14 Address C
15 Address B
16 Power (+5V)

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