I'm tryng to build this chip:
// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/01/Mux4Way16.hdl
/**
* 4-way 16-bit multiplexor:
* out = a if sel == 00
* b if sel == 01
* c if sel == 10
* d if sel == 11
*/
CHIP Mux4Way16 {
IN a[16], b[16], c[16], d[16], sel[2];
OUT out[16];
PARTS:
// Put your code here:
And that what i wrote ontil now -
PARTS:
// Put your code here:
Xor(a=sel[0], b=sel[1], out=finalSel);
Not(in=finalSel, out=notFinalSel);
Mux16(a=a, b=b, sel=finalSel, out=aAndB);
Mux16(a=c, b=d, sel=notFinalSel, out=cAndd);
Mux16(a=aAndB, b=cAndd, sel=sel[0], out=out);
}
And for some reason it's not working..
Screenshot from the HardwareSimulator
someone know why?
Your logic for selecting what input to pass through appears to be incorrect. You should test it by creating a truth table for finalSel, notFinalSel, aAndB, cAndd and out for each of the 4 control conditions.
In general, when doing these kinds of problems, the KISS principle holds; Keep It Simple and Stupid. You don't need any fancy logical manipulation of your sel[] bits, you can just use them directly. So once you get your version fixed (and understand where you went wrong), try doing a version that just consists of 3 Mux16's and nothing else. Once you have both versions working, you'll then understand the error that caused you to go down the wrong path in your first attempt, and that will be a valuable lesson going forward.
Have fun!
Related
I am trying to implement a system so that it retrieves sound and extracts the mfcc of it. I'd like to implement my own mfcc function because librosa library wasn't implemented in C and other implementations of mfcc extractions doesn't yield the same outputs as librosa library does.
So I wrote a code, however, when I would like create hanning window, program doesn't take a step further and always stays the same statement while debugging. The statement is below:
float *mul = malloc(sizeof(float)*fftsize);
The whole code is as follows:
float* hanning(int fftsize){
float *mul = malloc(sizeof(float)*fftsize);
for (int i = 0; i<fftsize; i++){
mul[i] = 0.5 * (1 - cos(2*PI*i/(fftsize-1)));
}
return mul;
}
I put an LCD code to all error handler functions in stm32f7xx_it.c file to determine which fault I'm facing, and I see that it is hard_fault.
So what's the problem? I hope the issue is explained clearly. Due to the privacy, I couldn't put here whole code. Sorry for that. Thx in advance for your response.
Edit: I am chaning malloc to normal array with a variable length array. But still it takes me to HardFault_Handler function. SCB->SHCSR returns sometimes 65535 and sometimes 1.
I am trying to make a 10-bit adder/subtractor. Right now, the logic works as intended. However, I am trying to set all bits to 0 iff there is overflow. To do this, I need to pass the output (tempOut) through a 10-bit Mux, but in doing so, am getting an error.
Here is the chip:
/**
* Adds or Subtracts two 10-bit values.
* Both inputs a and b are in SIGNED 2s complement format
* when sub == 0, the chip performs add i.e. out=a+b
* when sub == 1, the chip performs subtract i.e. out=a-b
* carry reflects the overflow calculated for 10-bit add/subtract in 2s complement
*/
CHIP AddSub10 {
IN a[10], b[10], sub;
OUT out[10],carry;
PARTS:
// If sub == 1, subtraction, else addition
// First RCA4
Not4(in=b[0..3], out=notB03);
Mux4(a=b[0..3], b=notB03, sel=sub, out=MuxOneOut);
RCA4(a=a[0..3], b=MuxOneOut, cin=sub, sum=tempOut[0..3], cout=cout03);
// Second RCA4
Not4(in=b[4..7], out=notB47);
Mux4(a=b[4..7], b=notB47, sel=sub, out=MuxTwoOut);
RCA4(a=a[4..7], b=MuxTwoOut, cin=cout03, sum=tempOut[4..7], cout=cout47);
// Third RCA4
Not4(in[0..1]=b[8..9], out=notB89);
Mux4(a[0..1]=b[8..9], b=notB89, sel=sub, out=MuxThreeOut);
RCA4(a[0..1]=a[8..9], b=MuxThreeOut, cin=cout47, sum[0..1]=tempOut[8..9], sum[0]=tempA, sum[1]=tempB, sum[2]=carry);
// FIXME, intended to solve overflow/underflow
Xor(a=tempA, b=tempB, out=overflow);
Mux10(a=tempOut, b=false, sel=overflow, out=out);
}
Instead of x[a..b]=tempOut[c..d] you need to use the form x[a..b]=tempVariableAtoB (creating a new internal bus) and combine these buses in your Mux10:
Mux10(a[0..3]=temp0to3, a[4..7]=temp4to7, ... );
Without knowing what line the compiler is complaining about, it is difficult to diagnose the problem. However, my best guess is that you can't use an arbitrary internal bus like tempOut because the compiler doesn't know how big it is when it first runs into it.
The compiler knows the size of the IN and OUT elements, and it knows the size of the inputs and outputs of a component. But it can't tell how big tempOut would be without parsing everything, and that's probably outside the scope of the compiler design.
I would suggest you refactor so that each RCA4 has a discrete output bus (ie: sum1, sum2, sum3). You can then use them and their individual bits as needed in the Xor and Mux10.
Whenever I input a = 1 and b = 1 I still get 0 and my inner pin of aAndNotb shows 1, however if I delete the Not gate I get a normally functioning Nand gate, what's the deal?
/**
* And gate:
* out = 1 if (a == 1 and b == 1)
* 0 otherwise
*/
CHIP And {
IN a, b;
OUT out;
PARTS:
// Put your code here:
Nand(a=a, b=b, out=aAndNotb);
Not(in=aAndNotb, out=out);
}
Given the symptoms you describe, the problem appears to be in your Not gate. Perhaps that component is not correctly implemented?
You can test this by implementing the Not gate directly using a Nand gate, which if you've implemented a Not gate, you already know how to do.
If that works, then the issue is the Not gate implementation. If it doesn't, then the issue is the wiring of the gates for some reason (but they look OK to me).
This question already has answers here:
ROL / ROR on variable using inline assembly in Objective-C
(2 answers)
Closed 9 years ago.
A few days ago, I asked the question below. Because I was in need of a quick answer, I added:
The code does not need to use inline assembly. However, I haven't found a way to do this using Objective-C / C++ / C instructions.
Today, I would like to learn something. So I ask the question again, looking for an answer using inline assembly.
I would like to perform ROR and ROL operations on variables in an Objective-C program. However, I can't manage it – I am not an assembly expert.
Here is what I have done so far:
uint8_t v1 = ....;
uint8_t v2 = ....; // v2 is either 1, 2, 3, 4 or 5
asm("ROR v1, v2");
the error I get is:
Unknown use of instruction mnemonic with unknown size suffix
How can I fix this?
A rotate is just two shifts - some bits go left, the others right - once you see this rotating is easy without assembly. The pattern is recognised by some compilers and compiled using the rotate instructions. See wikipedia for the code.
Update: Xcode 4.6.2 (others not tested) on x86-64 compiles the double shift + or to a rotate for 32 & 64 bit operands, for 8 & 16 bit operands the double shift + or is kept. Why? Maybe the compiler understands something about the performance of these instructions, maybe the just didn't optimise - but in general if you can avoid assembler do so, the compiler invariably knows best! Also using static inline on the functions, or using macros defined in the same way as the standard macro MAX (a macro has the advantage of adapting to the type of its operands), can be used to inline the operations.
Addendum after OP comment
Here is the i86_64 assembler as an example, for full details of how to use the asm construct start here.
First the non-assembler version:
static inline uint32 rotl32_i64(uint32 value, unsigned shift)
{
// assume shift is in range 0..31 or subtraction would be wrong
// however we know the compiler will spot the pattern and replace
// the expression with a single roll and there will be no subtraction
// so if the compiler changes this may break without:
// shift &= 0x1f;
return (value << shift) | (value >> (32 - shift));
}
void test_rotl32(uint32 value, unsigned shift)
{
uint32 shifted = rotl32_i64(value, shift);
NSLog(#"%8x <<< %u -> %8x", value & 0xFFFFFFFF, shift, shifted & 0xFFFFFFFF);
}
If you look at the assembler output for profiling (so the optimiser kicks in) in Xcode (Product > Generate Output > Assembly File, then select Profiling in the pop-up menu as the bottom of the window) you will see that rotl32_i64 is inlined into test_rotl32 and compiles down to a rotate (roll) instruction.
Now producing the assembler directly yourself is a bit more involved than for the ARM code FrankH showed. This is because to take a variable shift value a specific register, cl, must be used, so we need to give the compiler enough information to do that. Here goes:
static inline uint32 rotl32_i64_asm(uint32 value, unsigned shift)
{
// i64 - shift must be in register cl so create a register local assigned to cl
// no need to mask as i64 will do that
register uint8 cl asm ( "cl" ) = shift;
uint32 shifted;
// emit the rotate left long
// %n values are replaced by args:
// 0: "=r" (shifted) - any register (r), result(=), store in var (shifted)
// 1: "0" (value) - *same* register as %0 (0), load from var (value)
// 2: "r" (cl) - any register (r), load from var (cl - which is the cl register so this one is used)
__asm__ ("roll %2,%0" : "=r" (shifted) : "0" (value), "r" (cl));
return shifted;
}
Change test_rotl32 to call rotl32_i64_asm and check the assembly output again - it should be the same, i.e. the compiler did as well as we did.
Further note that if the commented out masking line in rotl32_i64 is included it essentially becomes rotl32 - the compiler will do the right thing for any architecture all for the cost of a single and instruction in the i64 version.
So asm is there is you need it, using it can be somewhat involved, and the compiler will invariably do as well or better by itself...
HTH
The 32bit rotate in ARM would be:
__asm__("MOV %0, %1, ROR %2\n" : "=r"(out) : "r"(in), "M"(N));
where N is required to be a compile-time constant.
But the output of the barrel shifter, whether used on a register or an immediate operand, is always a full-register-width; you can shift a constant 8-bit quantity to any position within a 32bit word, or - as here - shift/rotate the value in a 32bit register any which way.
But you cannot rotate 16bit or 8bit values within a register using a single ARM instruction. None such exists.
That's why the compiler, on ARM targets, when you use the "normal" (portable [Objective-]C/C++) code (in << xx) | (in >> (w - xx)) will create you one assembler instruction for a 32bit rotate, but at least two (a normal shift followed by a shifted or) for 8/16bit ones.
I wrote a simple program to understand how objective-c works. This program is the i-ching, an ancient divination based on six lines response, calculated after launching three coins for six times, and then build an hexagram which is the reponse.
I am stuck at this, that I am sure has simple solution. This is how I defined the lines, I know it's not the best design, but I am trying to use as much technology as possible.
Supposing you launch a coin, it can be 3 or 2 depending on the side, three coins result in possible value 6,7,8,9.
/**
* identifying a coin
*/
typedef enum {
head=3,
tail=2
} Coin;
/**
identify a line, three coins with a side value of
2 and 3 can result in 6,7,8,9
*/
typedef enum {
yinMutable=tail+tail+tail, // 6 --> 7
yang=tail+tail+head, // 7
yin=head+head+tail, // 8
yangMutable=head+head+head // 9 --> 8
} Line;
/**
The structure of hexagram from bottom "start" to top "end"
*/
typedef struct {
Line start;
Line officer;
Line transit;
Line minister;
Line lord;
Line end;
} Hexagram;
The first problem I encounter with this design is to assign a value at each line in Hexagram. The first launch should fill value in start, the second in officer....and so on.
But can be easily solved with a switch case...altough I don't like it.
1) First question: I wonder if there is some function like in javascript or c# like
foreach (property in Hexagram) that let me browse the properties in their declaration order, that would solve my problem.
2) Second question: as an alternative way I used an array of Line:
Controller.m
....
Line response[6]
....
-(id) buildHexagram:... {
for(i =0.....,i++).....
response[i]=throwCoins;
// I omit alloc view and the rest of the code...then
[myview buildSubview:response];
}
----------------------
subView.m
-(id) buildSubView:(Line[]) reponse {
NSLog(#"response[0]=%o",[response objectAtIndex[0]]); <--- HERE I GOT THE ERROR
}
but then, whit this solution I got an error EXC_BAD_ACCESS
So obviously I am misunderstanding how array works in objective-c or c !
In the hope I have made myself clear enough, can someone point out the solution to the first question, and what I am doing wrong in the second option.
thanks
Leonardo
You've created a C array of Line - to access the elements you need to use C style array accessors.
So instead of
[response objectAtIndex[0]]
use
response[0]