Data Flow Diagram for Library Management System

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Example of Memory Interfacing

Example 1

Consider a system in which the full memory space 64kb is utilized for EPROM memory. Interface the EPROM with 8085 processor.

• The memory capacity is 64 Kbytes. i.e

• 2^n = 64 x 1000 bytes where n = address lines.

• So, n = 16.

• In this system the entire 16 address lines of the processor are connected to address input pins of memory IC in order to address the internal locations of memory.

• The chip select (CS) pin of EPROM is permanently tied to logic low (i.e., tied to ground).

• Since the processor is connected to EPROM, the active low RD pin is connected to active low output enable pin of EPROM.

• The range of address for EPROM is 0000H to FFFFH.

Example 2

Consider a system in which the available 64kb memory space is equally divided between EPROM and RAM. Interface the EPROM and RAM with 8085 processor.

• Implement 32kb memory capacity of EPROM using single IC 27256.

• 32kb RAM capacity is implemented using single IC 62256.

• The 32kb memory requires 15 address lines and so the address lines A0 - A14 of the processor are connected to 15 address pins of both EPROM and RAM.

• The unused address line A15 is used as to chip select. If A15  is 1, it select RAM and If  A15  is 0, it select EPROM.

• Inverter is used for selecting the memory.

• The memory used is both Ram and EPROM, so the low RD and WR pins of processor are connected to low WE and OE pins of memory respectively.

• The address range of EPROM will be 0000H to 7FFFH and that of RAM will be 7FFFH to FFFFH.

Example 3

Consider a system in which 32kb memory space is implemented using four numbers of 8kb memory. Interface the EPROM and RAM with 8085 processor.

• The total memory capacity is 32Kb. So, let two number of 8kb n memory be EPROM and the remaining two numbers be RAM.

• Each 8kb memory requires 13 address lines and so the address lines A0- A12 of the processor are connected to 13 address pins of all the memory.

• The address lines and A13 - A14 can be decoded using a 2-to-4 decoder to generate four chip select signals.

• These four chip select signals can be used to select one of the four memory IC at any one time.

• The address line A15 is used as enable for decoder.

• The simplified schematic memory organization is shown.

• The address allotted to each memory IC is shown in following table.

Example 4

Consider a system in which the 64kb memory space is implemented using eight numbers of 8kb memory. Interface the EPROM and RAM with 8085 processor.

• The total memory capacity is 64Kb. So, let 4 numbers of 8Kb EPROM and 4 numbers of 8Kb RAM.

• Each 8kb memory requires 13 address lines. So the address line A0 - A12 of the processor are connected to 13address pins of all the memory lCs.

• The address lines A13, A14 and A]5 are decoded using a 3-to-8 coder to generate eight chip select signals. These eight chip select signals can be used to select one of the eight memories at any one time.

• The memory interfacing is shown in following figure.

• The address allocation for Interfacing 4 no. 8Kb EPROM and 4 no. 8Kb RAM with 8085 is,

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8085 Instruction Set in detail

8085 INSTRUCTION SET

click here for 8085 Instruction Set in details

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Now Know Ur Tops Girls

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Story by Jess Walter

Can a Corn

Ken took dialysis Tuesdays and Thursdays. It fell to Tommy after his
mom passed to check his stepdad out of the Pine Lodge Correctional
Facility. Drop him at the hospital. Take him back three hours later.
Ken groaned as he climbed up the truck. —Whatcha got there,
Tom?

Tommy looked over the backseat. —Pole and tackle.

—You goin’ fishin’ this weekend?

—I ain’t skydivin’.

Ken stared out his window. —You stop me by a store?
There was a downtown grocery sold Lotto, fortified wines, and
forties. Ken hopped out. Tommy spun radio stations till Ken come
back with a can a corn.


—Oh, no you ain’t, Ken.
—So got-damn tired, Tom. Can’t sit on that blood machine today.
—You’d rather die?
—I’d rather fish.
—No way, Ken.

He drove toward Sacred Heart. But when Tommy stopped at a red
light Ken reached back, got the pole and jumped out. Fine, Tommy
thought. Die. I don’t care. The old man walked toward the Spokane
River. Tommy pulled up next to him, reached over and rolled down
the passenger window.

—Get in the damn truck, Ken.

Ken ignored him.

—That pole ain’t even geared.

Ken walked, facing away.
Tommy drove alongside for another block. —Get in the truck,
Ken.
Ken turned down a one-way. Tommy couldn’t follow.
Fine. Stupid bastard. Tommy went back to work, but the only
thing in the pit was a brake job on some old lady’s Mercury: four
hundred in repairs on a shit-bucket worth three. Pissed, Tommy gave
the Mercury to Todd and drove back downtown.
He parked, got his tackle box from the truck and walked back
along the river. Found his stepfather under a bridge, dry pole next
to him.

Tommy gave him hook and weight.
Ken’s gray fingers shook.

—Give it here. Tommy weighted and hooked the line. He pulled

a can opener from the tackle box and opened Ken’s corn. Carefully,
Tommy pushed the steel hook into the corn’s paper skin until, with a
tiny spurt, it gave way.
He handed the old man back the pole. Ken cast it.
Half-hour later, Ken reeled in a dull catfish, yellow-eyed and spiny.
No fight in the thing at all. Almost like it didn’t mind.
Ken held it up. —Well I will be got-damned.
Tommy released the fish. It just kind of sank.
He dropped the old man at the front gate of the prison, his breathing already shallow. Rusty. He was so weak Tommy had to reach over
and pop his door.

—Hey that wadn’t a bad got-damn fish. All things considered. His
eyes were filming over already. —We should go again Tuesday.

—We gonna start playin’ catch now, too? Tommy asked.
Ken laughed. —I doubt it.
Then Tommy watched the dying old man pass through the metal
gate. The fucker.

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