diff --git a/sdk/bin/dzx7b.exe b/sdk/bin/dzx7b.exe
new file mode 100755
index 0000000..69b40c8
Binary files /dev/null and b/sdk/bin/dzx7b.exe differ
diff --git a/sdk/bin/dzx7b.exe.license b/sdk/bin/dzx7b.exe.license
new file mode 100644
index 0000000..331be09
--- /dev/null
+++ b/sdk/bin/dzx7b.exe.license
@@ -0,0 +1,11 @@
+SPDX-FileName: dzx7b.exe
+
+SPDX-FileType: BINARY
+
+SPDX-FileChecksum: SHA1: 1c1d766371864e10bfb5c95fa57d7598e8a6bf89
+
+SPDX-FileCopyrightText: Copyright (c) 2015 Einar Saukas. All rights reserved.
+
+SPDX-License-Identifier: BSD-3-clause
+
+SPDX-FileComment: dzx7b version 1.0 (2015) - LZ77/LZSS backwards decompressor.
diff --git a/sdk/src/zx7b/Makefile b/sdk/src/zx7b/Makefile
index 8799501..823104c 100644
--- a/sdk/src/zx7b/Makefile
+++ b/sdk/src/zx7b/Makefile
@@ -30,7 +30,9 @@ bindir		?= $(exec_prefix)/bin
 INSTALL		?= install
 INSTALL_PROGRAM	?= $(INSTALL)
 
-BINS		= zx7b$(EXESUFFIX)
+BINS=\
+ zx7b$(EXESUFFIX)\
+ dzx7b$(EXESUFFIX)
 
 .PHONY: all
 all: $(foreach t,$(BINS),build/$(t))
@@ -42,12 +44,18 @@ $(DESTDIR)$(bindir):
 build/zx7b$(EXESUFFIX): $(srcdir)/zx7b.c Makefile | build
 	$(CC) $(CFLAGS) -o $@ $<
 
+build/dzx7b$(EXESUFFIX): $(srcdir)/dzx7b.c Makefile | build
+	$(CC) $(CFLAGS) -o $@ $<
+
 .PHONY: install
 install: $(foreach t,$(BINS),$(DESTDIR)$(bindir)/$(t))
 
 $(DESTDIR)$(bindir)/zx7b$(EXESUFFIX): build/zx7b$(EXESUFFIX) | $(DESTDIR)$(bindir)
 	$(INSTALL_PROGRAM) $< $@
 
+$(DESTDIR)$(bindir)/dzx7b$(EXESUFFIX): build/dzx7b$(EXESUFFIX) | $(DESTDIR)$(bindir)
+	$(INSTALL_PROGRAM) $< $@
+
 .PHONY: uninstall
 uninstall:
 	rm -f $(foreach t,$(BINS),$(DESTDIR)$(bindir)/$(t))
diff --git a/sdk/src/zx7b/dzx7b.c b/sdk/src/zx7b/dzx7b.c
new file mode 100644
index 0000000..11fd4e6
--- /dev/null
+++ b/sdk/src/zx7b/dzx7b.c
@@ -0,0 +1,291 @@
+/*
+ * dzx7b - LZ77/LZSS backwards decompressor.
+ *
+ * Copyright (c) 2015 Einar Saukas. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * The name of its author may not be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * SPDX-FileCopyrightText: Copyright (c) 2015 Einar Saukas. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * SPDX-LicenseComments: License's text equals to one from https://directory.fsf.org/wiki/License:BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define PROGRAM "dzx7b"
+#define DESCRIPTION "LZ77/LZSS backwards decompressor."
+#define VERSION "1.0 (2015)"
+#define COPYRIGHT "Copyright (c) 2015 Einar Saukas. All rights reserved."
+#define LICENSE "Distributed under BSD 3-clause license."
+#define HOMEPAGE "https://github.com/antoniovillena/zx7b/"
+
+FILE *ifp;
+FILE *ofp;
+char *input_name;
+char *output_name;
+unsigned char *input_data;
+unsigned char *output_data;
+size_t input_index;
+size_t output_index;
+size_t input_size;
+size_t output_size;
+size_t partial_counter;
+size_t total_counter;
+int bit_mask;
+int bit_value;
+
+int read_byte() {
+    return input_data[input_index++];
+}
+
+int read_bit() {
+    bit_mask >>= 1;
+    if (bit_mask == 0) {
+        bit_mask = 128;
+        bit_value = read_byte();
+    }
+    return bit_value & bit_mask ? 1 : 0;
+}
+
+int read_elias_gamma() {
+    int i;
+    int value;
+
+    value = 1;
+    while (!read_bit()) {
+        value = value << 1 | read_bit();
+    }
+    if( (value&255)==255 )
+      value= -1;
+    return value;
+}
+
+int read_offset() {
+    int value;
+    int i;
+
+    value = read_byte();
+    if (value < 128) {
+        return value;
+    } else {
+        i = read_bit();
+        i = i << 1 | read_bit();
+        i = i << 1 | read_bit();
+        i = i << 1 | read_bit();
+        return (value & 127 | i << 7) + 128;
+    }
+}
+
+void write_byte(int value) {
+    output_data[output_index++] = value;
+}
+
+void write_bytes(int offset, int length) {
+    if (offset > output_size+output_index) {
+        fprintf(stderr, "Error: Invalid data in input file %s\n", input_name);
+        exit(1);
+    }
+    while (length-- > 0) {
+        write_byte(output_data[output_index-offset]);
+    }
+}
+
+void decompress() {
+    int length,i;
+
+    input_index = 0;
+    partial_counter = 0;
+    output_index = 0;
+    bit_mask = 0;
+
+    write_byte(read_byte());
+    while (1) {
+        if (!read_bit()) {
+            write_byte(read_byte());
+        } else {
+            length = read_elias_gamma()+1;
+            if (length == 0) {
+                return;
+            }
+            write_bytes(read_offset()+1, length);
+        }
+    }
+}
+
+void show_help() {
+    printf(
+        PROGRAM " version " VERSION " - " DESCRIPTION "\n"
+        COPYRIGHT "\n"
+        LICENSE "\n"
+        "Home page: " HOMEPAGE "\n"
+        "\n"
+        "Usage:\n"
+        "  " PROGRAM " [-f] input.zx7 [output]\n"
+        "\n"
+        "  -f       Force overwrite of output file\n"
+        "  output   Decompressed output file\n"
+    );
+}
+
+int main(int argc, char *argv[]) {
+    int forced_mode = 0;
+    int i;
+
+    /* process hidden optional parameters */
+    for (i = 1; i < argc && *argv[i] == '-'; i++) {
+        if (!strcmp(argv[i], "-f")) {
+            forced_mode = 1;
+        } else {
+            fprintf(stderr, "Error: Invalid parameter `%s\'\n", argv[i]);
+            exit(1);
+        }
+    }
+
+    /* determine output filename */
+    if (argc == i+1) {
+        input_name = argv[i];
+        input_size = strlen(input_name);
+        if (input_size > 4 && !strcmp(input_name+input_size-4, ".zx7")) {
+            output_name = (char *)malloc(input_size);
+            strcpy(output_name, input_name);
+            output_name[input_size-4] = '\0';
+        } else {
+            fprintf(stderr, "Error: Cannot infer output filename\n");
+            exit(1);
+        }
+    } else if (argc == i+2) {
+        input_name = argv[i];
+        output_name = argv[i+1];
+    } else {
+        show_help();
+        exit(1);
+    }
+
+    /* open input file */
+    ifp = fopen(input_name, "rb");
+    if (!ifp) {
+        fprintf(stderr, "Error: Cannot access input file %s\n", input_name);
+        exit(1);
+    }
+
+    /* determine input size */
+    fseek(ifp, 0L, SEEK_END);
+    input_size = ftell(ifp);
+    fseek(ifp, 0L, SEEK_SET);
+    if (!input_size) {
+        fprintf(stderr, "Error: Empty input file %s\n", argv[1]);
+        exit(1);
+    }
+
+    /* allocate input buffer */
+    input_data = (unsigned char *)malloc(input_size);
+    if (!input_data) {
+        fprintf(stderr, "Error: Insufficient memory\n");
+        exit(1);
+    }
+
+    /* read input file */
+    total_counter = 0;
+    do {
+        partial_counter = fread(input_data+total_counter, sizeof(char), input_size-total_counter, ifp);
+        total_counter += partial_counter;
+    } while ( partial_counter > 0 );
+
+    if (total_counter != input_size) {
+        fprintf(stderr, "Error: Cannot read input file %s\n", argv[1]);
+        exit(1);
+    }
+
+    /* check output file */
+    if (!forced_mode && fopen(output_name, "rb") != NULL) {
+        fprintf(stderr, "Error: Already existing output file %s\n", output_name);
+        exit(1);
+    }
+
+    /* create output file */
+    ofp = fopen(output_name, "wb");
+    if (!ofp) {
+        fprintf(stderr, "Error: Cannot create output file %s\n", output_name);
+        exit(1);
+    }
+
+    /* reverse input data */
+    for ( i= 0; i<input_size>>1; i++ ){
+        partial_counter = input_data[i];
+        input_data[i] = input_data[input_size-1-i];
+        input_data[input_size-1-i] = partial_counter;
+    }
+
+    /* calculate output file size and allocate memory */
+    output_size = 1;
+    read_byte();
+    while (1) {
+        if (!read_bit()) {
+            output_size++;
+            read_byte();
+        } else {
+            i = read_elias_gamma()+1;
+            if (i == 0) {
+                break;
+            }
+            read_offset();
+            output_size+= i;
+        }
+    }
+    output_data = (unsigned char *)malloc(output_size);
+    if (!output_data) {
+        fprintf(stderr, "Error: Insufficient memory\n");
+        exit(1);
+    }
+
+    /* decompress */
+    decompress();
+
+    /* reverse output data */
+    for ( i= 0; i<output_size>>1; i++ ) {
+      partial_counter= output_data[i];
+      output_data[i]= output_data[output_size-1-i];
+      output_data[output_size-1-i]= partial_counter;
+    }
+
+    /* write output file */
+    if (fwrite(output_data, sizeof(char), output_size, ofp) != output_size) {
+      fprintf(stderr, "Error: Cannot write output file %s\n", output_name);
+      exit(1);
+    }
+
+    /* close input file */
+    fclose(ifp);
+
+    /* close output file */
+    fclose(ofp);
+
+    /* done! */
+    printf("File `%s' converted from %lu to %lu bytes!\n",
+        output_name, (unsigned long)input_size, (unsigned long)output_size);
+
+    return 0;
+}