Change byte offset db address step 7 siemens

#CHANGE BYTE OFFSET DB ADDRESS STEP 7 SIEMENS CODE#

It turns out that the clock is probably 12MHz (if nop takes one cycle). In the end, it produced accurate measurements after looping a million times for each instruction type. They still had to branch to return instructions, but moving other instructions would change the distribution of return instructions. The hardest part of this was getting other instructions into the relative jump instructions: This involved stuffing instructions into arguments of other instructions, so that theyвЂ™re effectively shingled. I stuffed almost every instruction (up to registers) inside 256 bytes because I wanted to jump using a single jmp without doing 16-bit arithmetic, which would make the overhead higher and measurement harder. In order to find that out, I made this piece of 8051 code. Most 8051 instructions (barring maybe conditional jumps or div ab) on most cores have a constant number of cycles to be executed. One thing that prevented me from doing some micro-optimizations, however, is that I didnвЂ™t know the exact instruction timings: With this done, the fps is already at 34 fps, double of the previous value. Since this is an 8051, there is also no instruction cache to consider (IвЂ™ve never seen an 8051 with an instruction cache). Of course, since a byte will always be 8 bits on an 8051, it is faster to leave the JNC out and instead repeat the snippet 8 times.

#CHANGE BYTE OFFSET DB ADDRESS STEP 7 SIEMENS CODE#

In the innermost loop for the bit-banging, the code was Well, one easy thing to do is to just ignore the timings given by the data sheet and removing as many sleeps in the firmware as possible.ДЄnother thing drastically improving performance is loop unrolling: Of course, no one will be satisfied with just 17fps. Needless to say, the step of copying it to a buffer made it quite slow and I got somewhere along 7fps.ДЄfter moving the USB communication logic to a separate thread, eliminating the buffer and a bunch of micro-optimizations, I already increased the fps to 17fps. The host side was made using a PyQT application that sends the GET_REPORT requests and displays it inside a GUI. On the first try, I implemented it on the USB controller by storing the frame inside an XRAM buffer and reading that into the USB buffer. IвЂ™m not sure what exactly it does, but it does not work when skipping it. Getting the frame involves writing some values to a register and then reading 900 bytes from another register, all over SPI.ДЄ peculiarity about the USB controller is that, in order to set some I/O lines high or low, other bits have to be set or unset. The ADNS-9800 communicates over SPI, but the USB controller doesnвЂ™t have any native SPI ports, so it has to bit-bang the frames.Д¬ommunication involves registers, which can be read or written to by sending the address over SPI and then reading/writing the byte. Knowing that the hello world works, I could now go on to read frames from the sensor. This works without problem, and one gets to test both the firmware code and host code for invoking the special mode. MOV R2, #00 FFh at second batch of 8 bytes MOV R1, #(HELLO-PC_VA1) offset to 'hello world' string MOV R0, #08 number of bytes in buffer left MOV A, #03 report id, start of get_report MOV DPTR, #USB_OUT init dptr with USB buf address If the new mode is invoked, all interrupts are disabled and it is in a busy-wait loop waiting for USB packets.ДЇirst, of course, I wrote a simple hello world function that returns the string Hello, World! on a GET_REPORT: I made minimal modifications to the rest of the firmware (basically replacing one jump address) to invoke it.I copied the existing routines for the recovery USB mode to a separate location.To not risk break existing USB functionality IвЂ™m also quite used to 8051 assembly, so writing it poses no problem. When patching binaries, I find doing so in assembly is often advantageous to C (or PL/M-51, which is never advantageous) because it allows to modify existing functions or jump to the middle of a function. Hello World!ДЄs far as I know, the pre-existing USB controller firmware does not have any built-in function to read the frames, which is not really surprising. When looking into the ADNS-9800 datasheet, one is presented with the possibility of reading 30x30 greyscale images from the device, so I decided to just do that. reverse engineered parts of the sensor firmwareД«efore that, I also reverse engineered parts of the USB controller firmware of the mouse.reverse engineered the encryption used in the sensor (ADNS-9800) by staring at it really hard.в†ђ prev Reverse Engineering Firmware (in Mice)

Change byte offset db address step 7 siemens