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; FAT16 READER V.050303 - Armando Astarloa - 16 BIT VER.; APERT - UPV/EHU 2003 - DISTRIBUTED UNDER GPL LICENCE;; s0 -> TMP0 s1 -> TMP1 s2 -> TMP2 s3 -> TMP3 s4 -> TMP4 / SECTORS_PER_CLUSTER_READED s5 -> TMP5/SECTOR_WORDS_READED (256 TO 0); s6 -> TMP s7 -> SECTORS_PER_CLUSTER s8 -> CLUSTER_BEGIN_LBA0 (FAT) s9 -> CLUSTER_BEGIN_LBA1 sA -> CLUSTER_BEGIN_LBA2; sB -> CLUSTER_BEGIN_LBA3 sC -> ROOT_DIRECTORY_FIRST_CLUSTER0 (SUPPOSED LESS THAN 256 - USUALLY 2); sD -> data[7:0] WB MASTER sE -> data[15:8] WB MASTER sF -> acummulatorCONSTANT DATA_WB_OUT_7_0_MASTER, 00CONSTANT DATA_WB_OUT_15_8_MASTER, 01CONSTANT CONTROL_WB_OUT_MASTER, 02; D7 = D6 = D5 = D4 = D3 = D2 = A0_MASTER D1 = W_WE_MASTER D0 = STB_O_MASTER; STROBE_O_MASTER = 1 & W_WE=0 & WB_A0 = 0CONSTANT READ_SLAVE, 01; STROBE_O_MASTER = 1 & W_WE=1 & WB_A0 = 0CONSTANT WRITE_LBA_15_0, 03; STROBE_CF_READER = 1 & W_WE=1 & WB_A0 = 1CONSTANT WRITE_LBA_27_16, 07;--;-- SLAVE INTERFACE;--CONSTANT DATA_WB_OUT_7_0_SLAVE, 03CONSTANT DATA_WB_OUT_15_8_SLAVE, 04CONSTANT CONTROL_WB_OUT_SLAVE, 05; D7 = D6 = D5 D4 = D3 =; D2 = TAG1_ERROR; D1 = TAG0_WORD_AVAILABLE; D0 = ACK_O_SLAVECONSTANT ACK_O_SLAVE, 01CONSTANT TAG0_WORD_AVAILABLE, 02CONSTANT ERROR, 04;--;-- BUS CONTROL SIGNALS;--CONSTANT CONTROL_OUT_MASTER, 06; D7 = D6 = D5 = D4 = D3 = D2 = D1 =; D0 = WB_BUS_MASTER_WRITE_ENABLECONSTANT WB_BUS_MASTER_WRITE_ENABLE, 01CONSTANT CONTROL_OUT_SLAVE, 07; D7 = D6 = D5 = D4 = D3 = D2 = D1 =; D0 = WB_BUS_SLAVE_WRITE_ENABLECONSTANT WB_BUS_SLAVE_WRITE_ENABLE, 01;--;-- EXTERNAL REGISTERS FOR MORE DATA ALLOCATION (OTHER OPTION IS THE USE OF;-- ANOTHER BLOCK RAM IF IT IS AVALIABLE;--CONSTANT TMP_OUT_0, 08CONSTANT TMP_OUT_1, 09CONSTANT TMP_OUT_2, 0ACONSTANT TMP_OUT_3, 0BCONSTANT TMP_OUT_4, 0CCONSTANT TMP_OUT_5, 0DCONSTANT TMP_OUT_6, 0ECONSTANT TMP_OUT_7, 0F;--;-- INPUT PORTS;--;--;-- WISHBONE INTERFACE PORTS - INPUTS;--CONSTANT CONTROL_WB_IN_MASTER, 00; D7 = D6 = D5 = D4 = D3 = D2 =; D1 = ERROR_INPUT; D0 = ACK_I_MASTER;CONSTANT ACK_I_MASTER, 01CONSTANT ERROR_INPUT, 02CONSTANT CONTROL_WB_IN_SLAVE, 01; D7 = D6 = D5 = D4 = D3 = D2 =; D1 = -; D0 = STB_I_SLAVE;CONSTANT STB_I_SLAVE, 01;CONSTANT TAG0_FORCE_RESET,02;--;-- WISHBONE INTERFACE PORTS - INPUTS;--CONSTANT DATA_WB_IN_7_0_MASTER, 02CONSTANT DATA_WB_IN_15_8_MASTER, 03;--;-- EXTERNAL REGISTERS FOR MORE DATA ALLOCATION (OTHER OPTION IS THE USE OF;-- ANOTHER BLOCK RAM IF IT IS AVALIABLE;--CONSTANT TMP_IN_0, 04CONSTANT TMP_IN_1, 05CONSTANT TMP_IN_2, 06CONSTANT TMP_IN_3, 07CONSTANT TMP_IN_4, 08CONSTANT TMP_IN_5, 09CONSTANT TMP_IN_6, 0ACONSTANT TMP_IN_7, 0B;--;-- REGISTERS INITIALIZATION;--inicialization:;; WISHBONE INTERFACES INIZIALIZATION;LOAD sF, 00OUTPUT sF, DATA_WB_OUT_7_0_MASTEROUTPUT sF, DATA_WB_OUT_15_8_MASTEROUTPUT sF, DATA_WB_OUT_7_0_SLAVEOUTPUT sF, DATA_WB_OUT_15_8_SLAVEOUTPUT sF, CONTROL_WB_OUT_MASTEROUTPUT sF, CONTROL_WB_OUT_SLAVE;; WAIT FOR 410NS*3 (RESET DELAY)main:; PROCESS MASTER BOOT RECORDCALL process_master_boot_record; PROCESS ROOT DIRECTORYCALL process_root_directorystart:CALL cluster_2_lba;CALL write_lba_to_slave; sector_per_cluster -> sector_per_cluster_readedLOAD s4, s7; 256 -> (s6) SECTOR_WORDS_READEDCALL read_sectoridle:INPUT s6, CONTROL_WB_IN_SLAVE; CHECK STB INPUT; CONTROL_WB_IN_SLAVE-> TMP (s6); IF STB=1 GO TO THE NEXT STATE; IF STB=0 GO TO THE IDLE STATEAND s6, STB_I_SLAVEJUMP Z, idletransfer_word_to_master:CALL read_word_from_slaveCALL write_a_word_to_master; (SECTOR WORDS READED)-1SUB s5, 01check_sectors_words_readed:; IF sector_words_readed = 0 THEN READ_NEW_SECTOR; IF sector_words_readed > 0 THEN TRANSFER_WORD_TO_MASTERAND s5, s5CALL Z, check_sector_per_cluster_readedJUMP idletrack_new_cluster:; save the number of dummy reads that must be done when the fat sector will be readed; an are stored into s5 register; in s0 bits 6-0 of the cluster number (offset in the sector -> 256 words-fat16 entries); as is each read operation a word is readed no multiplication is needed; RESTORE CLUSTER NUMBERINPUT s0, TMP_IN_4INPUT s1, TMP_IN_5INPUT s2, TMP_IN_6INPUT s3, TMP_IN_7;; compose LBA address of the sector of the fat that must be readed;; SHIFT RIGHT 15-8 TO 7-0;LOAD sF, 07do_shift:SR0 s3; uses the carry for the MSB and stores LSB into the carrySRA s2SRA s1SRA s0SUB sF, 01JUMP NZ, do_shiftCALL add_load_fat_begin_lba; adds fat_begin_lba to the sector relative to the fat obteined from the cluster; now there is the lba of the FAT sector that must be readed in s0,s1,s2,s3CALL write_lba_to_slave; -- DUMMY READ OF THE WORDS OF THE SECTOR TILL THE ONE OF THE CLUSTER INTEGERINPUT sF, TMP_IN_4AND sF, 7FCALL do_dummy_reads_from_slave;; (sD) data[7:0] WB MASTER -> (s0) TEMPORAL REGISTER; (sE) data[7:0] WB MASTER -> (s1) TEMPORAL REGISTER; READ 2 BYTESCALL read_word_from_slaveLOAD s0, sDLOAD s1, sE; (sD) data[7:0] WB MASTER -> (s2) TEMPORAL REGISTER; (sE) data[7:0] WB MASTER -> (s3) TEMPORAL REGISTER; READ 2 BYTES;; CHECK IF ITS THE LAST ONE; CB3-CL2-CB1-CB0 IN FAT LITTLE ENDIAN ORDER CB0-CB1 CB2-CB3LOAD sF, sESUB sF, FFJUMP NZ, continue_file_processingLOAD sF, sDSUB sF, FFJUMP NZ, continue_file_processingfile_end:; infinite loop (file readed and tranferred)JUMP file_endcontinue_file_processing:; in s0,s1 is the cluster name; --; (SECTOR WORDS READED)= 256; sector_per_cluster -> sector_per_cluster_readedLOAD s2, 00LOAD s3, 00LOAD s4, s7CALL cluster_2_lbaCALL read_sectorRETURNadd_load_fat_begin_lba:INPUT sF, TMP_IN_0ADD s0, sFINPUT sF, TMP_IN_1ADDCY s1, sFINPUT sF, TMP_IN_2ADDCY s2, sFINPUT sF, TMP_IN_3ADDCY s3, sFRETURNcheck_sector_per_cluster_readed:; IF sector_per_cluster_readed = 0 THEN TRACK_NEW_CLUSTER; IF sector_per_cluster_readed > 0 THEN CHECK SECTOR WORDS READED; (sector_per_cluster_readed)-1; (SECTOR WORDS READED)= 256SUB s4, 01AND s4, s4JUMP Z, track_new_clusterread_new_sector:; (SECTOR WORDS READED)= 256; increment LBA; sector_per_cluster -> sector_per_cluster_readed-1ADD s0, 01ADDCY s1, 00ADDCY s2, 00ADDCY s3, 00read_sector:LOAD s5, 00CALL write_lba_to_slaveRETURN;; --; -- PROCESS MASTER BOOT RECORD (READ LBA BEGIN OF THE FIRST PARTITION); --process_master_boot_record:;; LOAD LBA FOR MBR READ;LOAD s0, 00LOAD s1, 00LOAD s2, 00LOAD s3, 00CALL write_lba_to_slave; information of the lba begin for the first partition; has an offset of 454 bytes -> 227(0xE3) wordsLOAD sF, E3CALL do_dummy_reads_from_slave;; --; -- MBR READ - Partition_LBA_Begin EXTRACTION; --;; (sD) data[7:0] WB MASTER -> (s0) lba; (sE) data[15:8] WB MASTER -> (s1) lba; (sD) data[7:0] WB MASTER -> (s2) lba; (sE) data[15:8] WB MASTER -> (s3) lbaCALL store_all_temporal_registersLOAD s8, s0LOAD s9, s1LOAD sA, s2LOAD sB, s3;; NOW IS THE LBA_BEGIN ON THE TMP REGISTERS; --------------------; READ FIRST SECTOR (FAT32 VOLUMEN ID) OF THE PARTITION; ---------------------CALL write_lba_to_slave;; READ -> SECTORS_PER_CLUSTER (OFFSET 0x0D);; offset 0x0D (13) => READ 13 bytes -> 6(0x06) words and drop LSB in the nextLOAD sF, 06CALL do_dummy_reads_from_slave;; (sE) data[7:0] WB MASTER -> (s7) SECTORS PER CLUSTERCALL read_word_from_slaveLOAD s7, sE;; READ -> Number_of_Reserved_Sectors (2 bytes) (OFFSET 0x0E);; offset 0x0E (14) => READ 2 bytes -> 1(0x01) words; (sD) data[15:8] WB MASTER -> (s6) TEMPORAL REGISTERCALL read_word_from_slaveLOAD s6, sD; (sE) data[7:0] WB MASTER -> (s4) TEMPORAL REGISTER;LOAD s4, sE;;fat_begin_lba = Partition_LBA_Begin + Number_of_Reserved_Sectors;ADD s8, s6ADDCY s9, s4ADDCY sA, 00ADDCY sB, 00; store fat_begin_lba in external registersOUTPUT s8, TMP_OUT_0OUTPUT s9, TMP_OUT_1OUTPUT sA, TMP_OUT_2OUTPUT sB, TMP_OUT_3;;cluster_begin_lba = Partition_LBA_Begin + Number_of_Reserved_Sectors +; (Number_of_FATs * Sectors_Per_FAT)+ RootDirSectors;;cluster_begin_lba = fat_begin_lba + (Number_of_FATs * Sectors_Per_FAT)+ RootDirSectors;; READ -> Number_of_Fats (OFFSET 0x10) (always 2);; offset 0x10 (16) => READ 2 bytes -> 1(0x01) words;; (sD) data[7:0] WB MASTER -> (s6) TEMPORAL REGISTERCALL read_word_from_slaveLOAD s6, sD;; FOR FAT16 => NUMBER OF SECTORS OCCUPIED BY THE ROOT DIRECTORY (BYTES_PER_SEC=512);; READ -> RootEntCnt (OFFSET 0x11) (FAT16 PROCESSING); RootDirSectors=((BPB_RootEntCnt*32)+(BPB_BytesPerSec-1))/BPB_BytesPerSec; offset 0x11 (17) => READ 1 bytes;; (sE) data[7:0] WB MASTER -> (s0) TEMPORAL REGISTERLOAD s0, sE; (sD) data[15:0] WB MASTER -> (sD) TEMPORAL REGISTER - offset 0x12 (18) => READ 1 bytesCALL read_word_from_slaveLOAD s1, sD; MULTIPLY BY 32 (100000) 5 SHIFTS TO THE LEFTLOAD sF, 05; LSB '0'mult_32:SL0 s0; CARRY -> LSB , MSB -> CARRYSLA s1SUB sF, 01JUMP NZ, mult_32;BPB_RootEntCnt*32+(BPB_BytesPerSec-1) 511 (0x1FF);ADD s0,FF (if rounds up => not necessary??);ADDCY s1,01;/BPB_BytesPerSec (512) (1000000000)9 SHIFTS TO THE RIGHTLOAD sF, 09div_512:; uses the carry for the MSB and stores LSB into the carrySR0 s1SRA s0SUB sF, 01JUMP NZ, div_512; ROUNDs UP;ADD s0,01;ADDCY s1,00;fat_begin_lba + RootDirSectorsADD s8, s0ADDCY s9, s1ADDCY sA, s2ADDCY sB, s3; READ -> Sectors_per_fat (OFFSET 0x24);; offset 0x16 (22) => READ 2 bytes -> 01(0x01) words;LOAD sF, 01CALL do_dummy_reads_from_slaveCALL store_all_temporal_registers; (Number_of_FATs * Sectors_Per_FAT); Number_of_FATs = 2 (10) . Do a shift to the left of the Sectors_Per_Fat; *** FAT16 = Sectors_per_fat(BPB_FATSz16); LSB '0'SL0 s0; CARRY -> LSB , MSB -> CARRYSLA s1;SLA s2 for fat16 only 2 bytes;SLA s3; fat_begin_lba + RootDirSectors + (Number_of_FATs * Sectors_Per_FAT)ADD s8, s0ADDCY s9, s1ADDCY sA, 00ADDCY sB, 00; cluster_begin_lba is stored in s8, s9, sA, SB;; FOR FAT16 ROOT DIRECTORY POSITION IS FIXED; root_first_lba = fat_begin_lba(in external regs) + (Number_of_FATs * Sectors_Per_FAT) (s0,s1,s2,s3);LOAD s2, 00LOAD s3, 00CALL add_load_fat_begin_lba; s0,s1,s2,s3 have Root directory begin lbaRETURNstore_all_temporal_registers:; READ 2 BYTESCALL read_word_from_slave; (sD) data[7:0] WB MASTER -> (s0) TEMPORAL REGISTER; (sE) data[7:0] WB MASTER -> (s1) TEMPORAL REGISTERLOAD s0, sDLOAD s1, sE; (sD) data[7:0] WB MASTER -> (s2) TEMPORAL REGISTER; (sE) data[7:0] WB MASTER -> (s3) TEMPORAL REGISTER; READ 2 BYTESCALL read_word_from_slaveLOAD s2, sDLOAD s3, sERETURNprocess_root_directory:; INPUT :; s0,s1,s2,s3 root directory lba (FAT16- FIXED); CALL cluster_2_lba; now s0,s1,s2,s3 contains the lba for the root directory; the first 32 byte record on the sector must be the root directory information; check if EOF (first byte of the 32 bytes is 0)CALL write_lba_to_slavecheck_for_a_file:CALL read_word_from_slave; (sD) data[7:0] WB MASTER -> (s6) TEMPORAL REGISTERLOAD s6, sDLOAD sF, s6AND sF, sF; if sF=0 the is not directory => errorJUMP Z, put_error_code;; check that is not a deleted entry;; (sD) data[7:0] WB MASTER -> (s6) TEMPORAL REGISTERLOAD sF, E5AND sF, s6; if s6=E5 is a deteled entry => check for new one (offset => sF)JUMP Z, check_next_directory_entrycheck_attribute:; ATTRIBUTE -> OFFSET Bh; check that is not a directory or LONG NAME; 00arshdv - DV for long name - D for directory; (sD) data[7:0] WB MASTER -> (s6) TEMPORAL REGISTERLOAD sF, 04CALL do_dummy_reads_from_slaveCALL read_word_from_slaveLOAD s6, sELOAD sF, 03AND sF, s6JUMP NZ, check_next_directory_entry_attribute; if s6=0 that is not a file => error;JUMP Z,check_next_directory_entry; check that is not a directory; check that is a file (short filename entry); in other case error;;; READ CLUSTER INFORMATION FOR THE FILE;CALL read_dir_cluster_hi_cluster_lowRETURNcheck_next_directory_entry:; go fwd 11 wordsLOAD sF, 05CALL do_dummy_reads_from_slavecheck_next_directory_entry_attribute:; go fwd 5 wordsLOAD sF, 0ACALL do_dummy_reads_from_slaveJUMP check_for_a_fileread_dir_cluster_hi_cluster_low:; INPUT :; before arrive here first two bytes of the directory; structure must be readed; OUTPUT :; s0,s1 : CLUS_LOW; s2,s3 : CLUS_HI;; READ -> cluster_HI (OFFSET 0x14);; offset 0x14 (20) => READ 18 bytes -> 9(0x09) words;LOAD sF, 04CALL do_dummy_reads_from_slave; (sD) data[7:0] WB MASTER -> s2; (sE) data[7:0] WB MASTER -> s3; READ 2 BYTESCALL read_word_from_slaveLOAD s2, sDLOAD s3, sEOUTPUT sE, TMP_OUT_7;; READ -> cluster_low(OFFSET 0x1A);; offset 0x1A (26) => READ 4 bytes -> 2(0x02) words;LOAD sF, 02CALL do_dummy_reads_from_slave; (sD) data[7:0] WB MASTER -> s0; (sE) data[7:0] WB MASTER -> s1; READ 2 BYTESCALL read_word_from_slaveLOAD s0, sDLOAD s1, sE; s0,s1 clus_low s3,s4 - clus_highRETURN; -- MBR READ OPERATION - LBA BEGIN DETERMINATION; '00' -> LBA_7_0,LBA_15_8,LBA_23_16,LD_LBA_27_24cluster_2_lba:; --; -- LBA ADDRESS DETERMINATION; --; lba_addr = cluster_begin_lba + (cluster_number - 2) * sectors_per_cluster;;; INPUT :; s0 : CLUSTER_NUMBER0, s1 : CLUSTER_NUMBER1, s2: CLUSTER_NUMBER2, s3 : CLUSTER_NUMBER3; OUTPUT :; s0 : LBA_ADDR_7_0 TMP1, s1 : LBA_ADDR_15_8, s2 : LBA_ADDR_24_16, s3 : LBA_ADDR_27_24;; cluster_number - 2;OUTPUT s0, TMP_OUT_4OUTPUT s1, TMP_OUT_5OUTPUT s2, TMP_OUT_6OUTPUT s3, TMP_OUT_7SUB s0, 02SUBCY s1, 00SUBCY s2, 00SUBCY s3, 00;; (cluster_number - 2) * sectors_per_cluster(s7);;; to perform the multiplication as sector_per_cluster is 2 multiple must be known; who many times must be shifted; (use sD as temporal register)LOAD sF, 08LOAD sD, s7multiply:SR0 sD; loop until detection of the 1 (2 multiple) - Add timeout!!!JUMP C, add_cluster_begin_lba; LSB '0'SL0 s0; CARRY -> LSB , MSB -> CARRYSLA s1SLA s2SLA s3JUMP multiplyadd_cluster_begin_lba:; lba_addr (TMP0,TMP1,TMP2,TMP3)= cluster_begin_lba + (cluster_number - 2) * sectors_per_cluster;ADD s0, s8ADDCY s1, s9ADDCY s2, sAADDCY s3, sBRETURN; --; -- WRITE A WORD INTO THE WB SLAVE INTERFACE (TO THE MASTER); --; INPUTS :; TMP0 : LSB TO DATA_WB_OUT_7_0_SLAVE; TMP1 : MSB TO DATA_WB_OUT_15_8_SLAVE;write_a_word_to_master:; TMP0 => DATA_WB_OUT_7_0_SLAVEOUTPUT sD, DATA_WB_OUT_7_0_SLAVE; 00 => DATA_WB_OUT_15_8_SLAVE;LOAD sF,00 -- 8 BIT VERSION;OUTPUT sF,DATA_WB_OUT_15_8_SLAVE -- 8 BIT VERSIONOUTPUT sE, DATA_WB_OUT_15_8_SLAVECALL write_a_byte_to_master;; CHECK STB INPUT | CONTROL_WB_IN_SLAVE-> TMP (s6);wait_strobe:INPUT s6, CONTROL_WB_IN_SLAVE;;AND s6, STB_I_SLAVEJUMP Z, wait_strobe; TMP1 => DATA_WB_OUT_7_0_SLAVE; OUTPUT sE,DATA_WB_OUT_7_0_SLAVE; 00 =>DATA_WB_OUT_15_8_SLAVE;LOAD sF,00 -- 8 BIT VERSION;OUTPUT sF,DATA_WB_OUT_15_8_SLAVE -- 8 BIT VERSION;CALL write_a_byte_to_master -- 8 BIT VERSIONRETURNwrite_a_byte_to_master:;; WB SLAVE WRITE ENABLE ACTIVE;LOAD sF, WB_BUS_SLAVE_WRITE_ENABLEOUTPUT sF, CONTROL_OUT_SLAVE;; ACK TO THE MASTER UNTIL STB FINISH;ack_to_the_master:LOAD sF, ACK_O_SLAVEOUTPUT sF, CONTROL_WB_OUT_SLAVE;;LOAD sF, 00OUTPUT sF, CONTROL_OUT_SLAVEOUTPUT sF, CONTROL_WB_OUT_SLAVERETURN; --; -- WRITE A LBA INTO THE WB MASTER INTERFACE (TO THE SLAVE); --; INPUTS :; TMP0 : LBA_ADDR_7_0, TMP1 : LBA_ADDR_15_8, TMP2 : LBA_ADDR_24_16, TMP3 : LBA_ADDR_27_24;;write_lba_to_slave:;; WB MASTER WRITE ENABLE ACTIVE;LOAD sF, WB_BUS_MASTER_WRITE_ENABLEOUTPUT sF, CONTROL_OUT_MASTER;write_lba_15_0_to_slave:;; TMP0 : LBA_ADDR_7_0 (s0) => DATA_WB_OUT_7_0_MASTER; TMP1 : LBA_ADDR_15_8 (s1) => DATA_WB_OUT_15_8_MASTER;OUTPUT s0, DATA_WB_OUT_7_0_MASTEROUTPUT s1, DATA_WB_OUT_15_8_MASTER;; --; -- WRITE LBA 15-0 TO THE SLAVE; --;; WB_CONTROL_OUT_MASTER; W_WE_MASTER = 1; STB_O_MASTER = 1; A0 = 0;LOAD sF, WRITE_LBA_15_0OUTPUT sF, CONTROL_WB_OUT_MASTER;; WAIT FOR THE ACK;CALL wait_for_the_ack;write_lba_27_16_to_slave:;; TMP2 : LBA_ADDR_23_16 (s2) => DATA_WB_OUT_7_0_MASTER; TMP3 : LBA_ADDR_27_24 (s3) => DATA_WB_OUT_15_8_MASTER;OUTPUT s2, DATA_WB_OUT_7_0_MASTEROUTPUT s3, DATA_WB_OUT_15_8_MASTER; --; -- WRITE LBA 27-16 TO THE SLAVE; --; WB_CONTROL_OUT_MASTER; W_WE_MASTER = 1; STB_O_MASTER = 1; A0 = 0;LOAD sF, WRITE_LBA_27_16OUTPUT sF, CONTROL_WB_OUT_MASTER;; WAIT FOR THE ACK;CALL wait_for_the_ack; --; -- FINISH WRITE OPERATION ON THE MASTER WB INTERFACE; --;; WB_CONTROL_OUT_MASTER; W_WE_MASTER = 0; STB_O_MASTER = 0; A0 = 0;LOAD sF, 00OUTPUT sF, CONTROL_WB_OUT_MASTEROUTPUT sF, CONTROL_OUT_MASTERRETURN; --; -- PERFORM DUMMY READS FROM THE WB SLAVE; --; -- IN sF ARE THE NUMBER OF WORDS THAT MUST BE READED; --do_dummy_reads_from_slave:LOAD s6, sFdummy_reads_from_slave:CALL read_word_from_slaveSUB s6, 01JUMP NZ, dummy_reads_from_slaveRETURN; --; -- PERFORM A WORD READING FROM THE WB SLAVE; --read_word_from_slave:; WB_CONTROL_OUT_MASTER; W_WE_MASTER = 0; STB_O_MASTER = 1; A0 = 0; wait stateLOAD sF, READ_SLAVEOUTPUT sF, CONTROL_WB_OUT_MASTER;; WAIT FOR THE ACK;; CALL wait_for_the_ack;JUMP Z,data_available_on_wb_masterwait_for_the_ack:;; CONTROL_WB_IN_MASTER -> TMP (s6);INPUT sF, CONTROL_WB_IN_MASTER;AND sF, ACK_I_MASTERJUMP Z, wait_for_the_ackdata_available_on_wb_master:; This part is not necessary in write operations; DATA_WB_IN_7_0_MASTER -> (sD) data[7:0] WB MASTER; DATA_WB_IN_15_8_MASTER -> (sE) data[15:8] WB MASTERINPUT sD, DATA_WB_IN_7_0_MASTERINPUT sE, DATA_WB_IN_15_8_MASTER; DISABLE RD/WR OPERATION REQUESTLOAD sF, 00OUTPUT sF, CONTROL_WB_OUT_MASTERRETURNput_error_code:LOAD sF, ERROROUTPUT sF, CONTROL_WB_OUT_SLAVEJUMP put_error_codeinterrupt:RETURNI ENABLE
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