Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Microprocessor Lab: Adding Battery Backup and I/O Decoder to a Microprocessor Circuit, Lab Reports of Physics

University of Washington (UW) - SeattlePhysics

In this document, students are provided with instructions for adding battery backup and an i/o decoder to a microprocessor lab circuit. The lab manual explains the purpose of each modification, the components required, and the steps to implement them. The document also includes important notes on resetting the cpu, checking unused inputs, and preventing glitches when writing to memory.

Typology: Lab Reports

Pre 2010

Uploaded on 03/11/2009

koofers-user-78n
koofers-user-78n 🇺🇸

8 documents

1 / 3

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Microprocessor Lab - Add Battery Backup, I/O Decoder
Physics 335
May 1, 2007
In this lab, you will add circuitry to allow the CPU to read the keypad directly and to allow
the CPU to write to the data display chips ONLY when it has something useful to say. Up until
now, the display chips showed whatever was on the data lines, and the keypad only wrote to the
memory. This leads, of course, to lots of information being displayed that’s of no use to a user
of such a circuit, such as opcodes as the machine executes it’s program. To understand what’s
happening, it is useful to read p. 459 - 462 of the lab manual before beginning.
There is not as much wiring this week as last week, but there is more programming. If you
were behind a little last week, you may again catch up a bit this one. As always, wire neatly or
pay later. Some boards look pretty manageable to troubleshoot... some are probably a nightmare.
BEFORE BEGINNING, NOW IS A GOOD TIME TO CHECK THAT ALL UNUSED IN-
PUTS OF THE ’HC CHIPS YOU INSTALLED IN THE LAST 3 WEEKS ARE TIED TO +5v.
I’ve noted that many inputs, especially on the HC74’s have been left floating. You may get by
with this for awhile, but this can also destroy the chip and/or cause bezarre circuit behavior. I
have intentionally left a few floating on the demo board (in spite of the fact that this is a bad idea
overall) so that it’s not quite as confusing to trace wires if you go up to look at it. I’ll be tidying
up, however, as well. Leaving HC inputs floating is bad form, even if your circuit works.
Also note that it is a good idea to RESET the CPU (via the keypad RESET) EACH TIME
you turn on power. Failure to do this can sometimes leave the CPU in an unresponsive state and
bizarre behavior sometimes ensues. RESETTING the CPU makes sure that all registers are set to
a known startup state and don’t lead to any oddities.
19.1 (p. 472) Do this section following the lab maual instructions. The 3 Volt supply is
located on the underside of the breadboard and is brought out to the binding post marked as such.
Replace the 6263 diodes in the circuit diagram with 1N5817 diodes from your parts cabinets or on
the front table in the lab. This battery backup will save any programs you meticulously type in by
hand from being lost when power is turned off. DISCONNECT the direct power connection from
+5 Volts that you had previously for the RAM. If you put in miswire on this, it’s possible to short
out a batter occasionally leading to a spectacular failure
Be careful with all your diodes and transistor that you connect them correctly. Remember that
the band on the diode, when conducting, is toward the negative side. In our case, the band should
be “toward” the memory and “away from” the power sources. Notice also, the zener’s direction... In
the case of the zener diode, the band is toward the positive side. Look on the laminated datasheets
or in the back of your lab manual for the pinout for the 2N3906 transistor. The “arrow” of the
transistor in Figure L19.3 points from the Emitter (E) to the Base (B) and the 10K resistor and
CS2 connect to the memory.
1
pf3

Partial preview of the text

Download Microprocessor Lab: Adding Battery Backup and I/O Decoder to a Microprocessor Circuit and more Lab Reports Physics in PDF only on Docsity!

Microprocessor Lab - Add Battery Backup, I/O Decoder

Physics 335

May 1, 2007

In this lab, you will add circuitry to allow the CPU to read the keypad directly and to allow the CPU to write to the data display chips ONLY when it has something useful to say. Up until now, the display chips showed whatever was on the data lines, and the keypad only wrote to the memory. This leads, of course, to lots of information being displayed that’s of no use to a user of such a circuit, such as opcodes as the machine executes it’s program. To understand what’s happening, it is useful to read p. 459 - 462 of the lab manual before beginning. There is not as much wiring this week as last week, but there is more programming. If you were behind a little last week, you may again catch up a bit this one. As always, wire neatly or pay later. Some boards look pretty manageable to troubleshoot... some are probably a nightmare.

BEFORE BEGINNING, NOW IS A GOOD TIME TO CHECK THAT ALL UNUSED IN-

PUTS OF THE ’HC CHIPS YOU INSTALLED IN THE LAST 3 WEEKS ARE TIED TO +5v. I’ve noted that many inputs, especially on the HC74’s have been left floating. You may get by with this for awhile, but this can also destroy the chip and/or cause bezarre circuit behavior. I have intentionally left a few floating on the demo board (in spite of the fact that this is a bad idea overall) so that it’s not quite as confusing to trace wires if you go up to look at it. I’ll be tidying up, however, as well. Leaving HC inputs floating is bad form, even if your circuit works. Also note that it is a good idea to RESET the CPU (via the keypad RESET) EACH TIME you turn on power. Failure to do this can sometimes leave the CPU in an unresponsive state and bizarre behavior sometimes ensues. RESETTING the CPU makes sure that all registers are set to a known startup state and don’t lead to any oddities.

19.1 (p. 472) Do this section following the lab maual instructions. The 3 Volt supply is located on the underside of the breadboard and is brought out to the binding post marked as such. Replace the 6263 diodes in the circuit diagram with 1N5817 diodes from your parts cabinets or on the front table in the lab. This battery backup will save any programs you meticulously type in by hand from being lost when power is turned off. DISCONNECT the direct power connection from +5 Volts that you had previously for the RAM. If you put in miswire on this, it’s possible to short out a batter occasionally leading to a spectacular failure Be careful with all your diodes and transistor that you connect them correctly. Remember that the band on the diode, when conducting, is toward the negative side. In our case, the band should be “toward” the memory and “away from” the power sources. Notice also, the zener’s direction... In the case of the zener diode, the band is toward the positive side. Look on the laminated datasheets or in the back of your lab manual for the pinout for the 2N3906 transistor. The “arrow” of the transistor in Figure L19.3 points from the Emitter (E) to the Base (B) and the 10K resistor and CS2 connect to the memory.

19.2 Do as instructed. Replace the 1N748 Zener diode in the circuit diagram with a 1N Zener (also 3.9V) from your cabinet or the front table in the lab. Be sure to run a +5 volt line directly from close to the 5V binding post to close to the transistor. This circuitry prevents glitches from writing to memroy when you turn power on and off.

19-3 Do as instructed in the manual. Look at the assmbled breadboard for hints. Before testing the I/O decoder, take a minute to figure out what it is supposed to do: Output n goes LO (true) only when ALL THREE enable conditions are true AND when binary n appears on S2 S1 S0. The enables are true when A15 is high (address 8000H - 8FFFH), when FC1 and FC of the CPU are not both high (when they are, this means the CPU needs to service an interupt), and when DS* is LO (the CPU is sending or receiving data). For example, when the CPU wants to write data to memory location 8000H, OUTPUT0* goes LO (R/W=0, A1=0, A0=0), while when it wants to read data from 8000H, INPORT0 goes LO. Because we are not decoding A2 and up, reading and writing to 8004H, 8008H, etc will be the same as reading or writing to 8000H. This is becuase only the values of A1 and A0 are being looked at.Test the decoder as instructed. Be sure to load the first eight memory locations with 00 00 20 00 00 00 01 10. (Do you see why?) You needn’t do the full speed optional test. On this same note, read the note on word sized pointer definitions. Note that on line 110 we move a word sized chunk of information (16 bits) into a LONG WORD address (32 bits). What to do, what to do... we have to many bits... The processor deals with this little dellema by “Sign Extending” the upper word of the address from the MSB of the lower word. Since the MSB of our lower byte is 1, this sign extends to FFFF8000, which is just ducky for the processor. It writes this value into the address register perfectly happily. But alas, our compiler only allows for 16MBytes of memory, so anything above 00FFFFFF is strickly verboten as far as it is concerned. Besides, we’re only looking at the Address lines up to A15... We DON’T CARE what the others are. So again, hardware is king. The kicker here for you may be if you try to simulate it. It will compile the code just fine, but as the address listed is out of memory range, will give you an error. The compiled code will work just fine (compare with what’s in the book if you like), but if this error bothers you, your free to use a long word instead for your movea command (movea.l)... You’ll just be typing a little more.

19.4 Do as instructed in the manual. Again, refer to the assembled breadboard to place your chips and wires. Here, you will be replacing the ENABLE pins on all four data display chips and the BLANKING pins on the rightmost two data display chips, so BE SURE TO REMOVE THE PREVIOUS CONNECTIONS TO THESE PINS. This circuitry allows the leftmost data display digits to show what is on the data lines when you “single step”, have control of the bus (busgive* is true), or when the CPU does a word (16 bit) write to 8000H.

19.5 Do as instructed. You should read throught the entire exercise before beginning. Put your boards back to the side of the room when you’re done. I recomment putting the keypad on top of your board or to the side (even better), rather than underneath, least your keypad accidentally short out your batteries. Also, do NOT bother unplugging your keypad from the breadboard. It will cause you more harm than good. I think sometimes people unplug worried that they will accidentally bump a key and overwrite part of their program, but remember – You added back circuitry that keep the info in the memory but disabled the memory via the chipselect lines, so you won’t overwrite it if you’ve wired carefully.