Lab-9
9-MAKING RAM
The purpose of this lab is to build the circuit of the Random Access Memory (RAM) of SAP-1.
Components Required
• 16*4 Static RAM, 74LS189-----------------(2)
• Connecting Wires
16*4 Static RAM
The chips used here are 74LS189s. Each chip is a 16*4 static RAM. Together, they give us a 16*8 read-
write memory. S3 is a data switch register (8-bit), and S4 is a read-write switch (a push-button switch).
To program the memory, S2 is put in the PROG position, this takes the CE input low (pin 2). The address
and data switches are then set to the correct address and data words. A momentary push of the read-
write switch loads the memory. After the program and data are in memory, the RUN-PROG switch (S2) is
put in the RUN position in preparation for the computer run.
Procedure
Connect the circuit as shown in the figure.
What will be the Outcome?
By keeping the switch of Multiplexer on PROG mode, address the RAM location through switches A
0
to A
3
,
and then write some inverted instruction by keeping the switches of RAM on Write and PROG mode.
Afterwards try to read the instruction by keeping the switch of Multiplexer on RUN mode and using the
higher nibble for addressing the specific location and keeping the switches of RAM on READ and RUN
mode.
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