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remove redundant CLB command,

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update program3 using fixes from program2
This commit is contained in:
Arthur Lu 2022-08-18 03:41:07 +00:00
parent 36e5abab60
commit 2d17abe39e
2 changed files with 15 additions and 14 deletions
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1
firmware/program2.asm
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@ -82,7 +82,6 @@ tap_init: LDI #d64
main_loop: LDI lfsr_routine // load address for the lfsr_routine label main_loop: LDI lfsr_routine // load address for the lfsr_routine label
JAL r0 // jump to the lfsr_routine label JAL r0 // jump to the lfsr_routine label
LDW r11 // load the next ciphertext byte LDW r11 // load the next ciphertext byte
CLB r0 // clear leading bit because we do not expect errors
XOR r7 // bitwise XOR the current state with ciphertext space to generate plaintext XOR r7 // bitwise XOR the current state with ciphertext space to generate plaintext
CLB r0 // clear the leading bit of the plaintext as in requirements CLB r0 // clear the leading bit of the plaintext as in requirements
STW r12 // store plaintext to write pointer STW r12 // store plaintext to write pointer

28
firmware/program3.asm
View File

@ -1,5 +1,5 @@
// Program 3 register use map: // Program 2 register use map:
// r0 is the accumulator, r1 and r2 is often used to cache temp values // r0 is the accumulator, r1 is often used to cache temp values
// r5 is the TAP LUT link register // r5 is the TAP LUT link register
// r6 is LFSR tap pattern // r6 is LFSR tap pattern
// r7 is LFSR state value // r7 is LFSR state value
@ -34,20 +34,20 @@ tap_init: LDI #d64
PUT r11 // set read pointer to 64 PUT r11 // set read pointer to 64
LDI #d0 LDI #d0
PUT r12 // set write pointer to 0 PUT r12 // set write pointer to 0
LDI #d10 LDI #d9
PUT r8 // load 10 into preamble counter PUT r8 // load 9 into preamble counter
LDI #d64 LDI #d64
PUT r9 // load 64 (total encryption length) to r9 PUT r9 // load 64 (total encryption length) to r9
LDI done LDI done
NXT r10 // decrement tap selection by 1, starts at 9 for the first iteration NXT r10 // decrement tap selection by 1, starts at 9 for the first iteration
JEZ r0 // if no more taps left that didn't work, raise the done flag JEZ r0 // if no more taps left that didn't work, raise the done flag
LDI tap_init LDI lut_return
PUT r5 // put the tap_loop address in r5 PUT r5 // put the tap_loop address in r5
LDI tap_lut LDI tap_lut
ADD r10 ADD r10
ADD r10 // add 2*tap select to tap_lut location, results in location of selected tap pattern ADD r10 // add 2*tap select to tap_lut location, results in location of selected tap pattern
JMP r0 // jump to LUT, which loads the tap pattern into r0 JMP r0 // jump to LUT, which loads the tap pattern into r0
PUT r6 // tap pattern now in r6 lut_return: PUT r6 // tap pattern now in r6
LDW r11 // get the first preamble character LDW r11 // get the first preamble character
PUT r1 // put cipher text into r1 PUT r1 // put cipher text into r1
LDI #d32 // load expected space character LDI #d32 // load expected space character
@ -59,13 +59,14 @@ tap_init: LDI #d64
NXT r9 // decrement total encryption chars remaining NXT r9 // decrement total encryption chars remaining
tap_loop: LDI lfsr_routine tap_loop: LDI lfsr_routine
JAL r0 // jump to lfsr routine which calculates next state in r7 JAL r0 // jump to lfsr routine which calculates next state in r7
LDI #d0 // load space char expected plaintext LDI #d32 // load space char expected plaintext
XOR r7 XOR r7
CLB r0 // clear leading bit in the expected ciphertext CLB r0 // clear leading bit in the expected ciphertext
PUT r1 // store expected cipher text in r1 PUT r1 // store expected cipher text in r1
LDI tap_init LDI tap_init
PUT r2 // load the outer loop top into r2 PUT r2 // load the outer loop top into r2
LDW r11 // load actual ciphertext LDW r11 // load actual ciphertext
CLB r0 // clear leading bit for r0 since we do not expect any errors for this program
SUB r1 // subtract actual from expected, result of 0 means matching SUB r1 // subtract actual from expected, result of 0 means matching
JNZ r2 // jump to outer loop (picks new tap pattern) if the actual cipher was not equal to the expected JNZ r2 // jump to outer loop (picks new tap pattern) if the actual cipher was not equal to the expected
LDI #d32 // load preamble char LDI #d32 // load preamble char
@ -78,21 +79,22 @@ tap_init: LDI #d64
JEZ r0 // if r8 (preamble counter) is zero, then all preamble have matched and current tap pattern is correct, jump to main loop JEZ r0 // if r8 (preamble counter) is zero, then all preamble have matched and current tap pattern is correct, jump to main loop
LDI tap_loop LDI tap_loop
JMP r0 // jump to tap_loop if characters matched but preamble is not over JMP r0 // jump to tap_loop if characters matched but preamble is not over
main_loop: LDI correct main_loop: LDI lfsr_routine // load address for the lfsr_routine label
JAL r0 // jump to the lfsr_routine label
LDI correct
PUT r1 // put correct handle address in r1 PUT r1 // put correct handle address in r1
LDW r11 // load the next ciphertext byte LDW r11 // load the next ciphertext byte
CHK r0 // check ciphertext for error CHK r0 // check ciphertext for error
JEZ r1 // if no error, jump to correct, otherwise continue to error handling JEZ r1 // if no error goto correct handler, otherwise continue to error handler
error: LDI #x80 // load error flag character into r0 error: LDI #x80 // load error flag character into r0
STW r12 // store error flag to write pointer STW r12 // store error flag to write pointer
LDI common LDI common
JMP r0 // jump out of error handling, to common operations after writing JMP r0 // jump out of error handling, to common operations after writing
correct: XOR r7 // bitwise XOR the current state with ciphertext space to generate plaintext correct: CLB r0 // clear leading bit because we do not expect errors
XOR r7 // bitwise XOR the current state with ciphertext space to generate plaintext
CLB r0 // clear the leading bit of the plaintext as in requirements CLB r0 // clear the leading bit of the plaintext as in requirements
STW r12 // store plaintext to write pointer STW r12 // store plaintext to write pointer
common: LDI lfsr_routine // load address for the lfsr_routine label common: NXT r11 // increment read pointer
JAL r0 // jump to the lfsr_routine label
NXT r11 // increment read pointer
NXT r12 // increment write pointer NXT r12 // increment write pointer
LDI done // load address of label done LDI done // load address of label done
NXT r9 // decrement number of remaining plaintext chars NXT r9 // decrement number of remaining plaintext chars