SAP Computer RAM

Ram

The RAM is a X 8 static TTL RAM. We can program the RAM by means of the address and data switch registers. This allows us to store a program and data in the memory before a computer run.

During a computer run, the RAM receive 4-bit addresses from MAR and a read operation is performed. The instuction or data word stored in the RAM are placed on the W bus for use in some other part of the Comput Er.

1 LibraryIEEE;2  Useieee.std_logic_1164. All;3  UseIeee.numeric_std. All;4 5 EntityRom_16_8 is6 Port7 (8     READ:inch     Std_logic; --! Active Low Enable ROMSignal, (tri-State )9ADDRESS:inch     Std_logic_vector(3 Downto 0); --!4-bitROM address bits from MARTenData_out: out    Std_logic_vector(7 Downto 0)     --!8-bitRomOutputWord toWBus One );  A EndRom_16_8; -  - ArchitectureBeh ofRom_16_8 is the  - typeMem is Array(0  to  the) of Std_logic_vector(7 Downto 0) ; - SignalRom:mem; -  + begin--! This program works as Follow:21--!--! Load 5 to AC (memory content of 9)--! Output 5 (content of AC)--! ADD 7 (Memory content of ten) to 5 (AC content)--! Output (content of AC)--! ADD 3 (Memory content of one) to (AC content)--! Subtract 4 (memory content of) from (AC content)--! Output One (content of AC) inRom <= ( -             0="00001001",-LDA 9h ... Load AC with the content of memory location 9 to             1="11101111",-- out +             2="00011010",--ADD Ah ... ADD the contents of memory location A to the AC content and replace the AC -             3="11101111",-- out the             4="00011011",--ADD Bh ... ADD the contents of memory location B to the AC content and replace the AC *             5="00101100",--SUB Ch ... Sub the contents of memory location C from the AC content and replace the AC $             6="11101111",-- outPanax Notoginseng             7="11111111",--HLT -             8="11111111" , the             9="00000101",--5 +             Ten="00000111",--7 A              One="00000011",--3 the              A="00000100",--4 +              -="11111111" ,  -              -="11111111" ,  $              the="11111111" ); $  -     Process(READ, ADDRESS) -     begin the         if READ='0'  Then -Data_out <=Rom (to_integer(unsigned(ADDRESS)));Wuyi          Else theData_out <= (data_out' Range ='Z'); -         End if;  Wu    End Process ; -     About EndBeh

SAP Computer RAM