diff --git a/common.mk b/common.mk
index 2aaf69b..20f52e6 100644
--- a/common.mk
+++ b/common.mk
@@ -160,12 +160,18 @@ sh7091/sh7091.hpp: regs/sh7091.csv regs/gen/sh7091.py
 sh7091/sh7091_bits.hpp: regs/sh7091_bits.csv regs/gen/core_bits.py
 	python regs/gen/core_bits.py $< > $@
 
+gdrom/gdrom.hpp: regs/gdrom.csv regs/gen/gdrom.py
+	python regs/gen/gdrom.py $< gdrom > $@
+
 gdrom/gdrom_bits.hpp: regs/gdrom_bits.csv regs/gen/core_bits.py
 	python regs/gen/core_bits.py $< gdrom > $@
 
 gdrom/command_packet_format.hpp: regs/gdrom_command_packet_format.csv regs/gen/gdrom_command_packet_format.py regs/gen/generic_sparse_struct.py
 	python regs/gen/gdrom_command_packet_format.py $< gdrom_command_packet_format > $@
 
+iso9660/%.hpp: iso9660/%.csv iso9660/byte_position.py
+	python iso9660/byte_position.py $< > $@
+
 clean:
 	find -P \
 		-regextype posix-egrep \
diff --git a/example/example.mk b/example/example.mk
index e77505e..847933c 100644
--- a/example/example.mk
+++ b/example/example.mk
@@ -357,3 +357,10 @@ GDROM_TEST_OBJ = \
 
 example/gdrom_test.elf: LDSCRIPT = $(LIB)/alt.lds
 example/gdrom_test.elf: $(START_OBJ) $(GDROM_TEST_OBJ)
+
+GDROM_ISO9660_OBJ = \
+	example/gdrom_iso9660.o \
+	sh7091/serial.o
+
+example/gdrom_iso9660.elf: LDSCRIPT = $(LIB)/alt.lds
+example/gdrom_iso9660.elf: $(START_OBJ) $(GDROM_ISO9660_OBJ)
diff --git a/example/gdrom_iso9660.cpp b/example/gdrom_iso9660.cpp
new file mode 100644
index 0000000..ec2264e
--- /dev/null
+++ b/example/gdrom_iso9660.cpp
@@ -0,0 +1,213 @@
+#include <cstdint>
+
+#include "memorymap.hpp"
+#include "systembus.hpp"
+#include "sh7091/serial.hpp"
+#include "gdrom/gdrom.hpp"
+#include "gdrom/gdrom_bits.hpp"
+#include "gdrom/command_packet_format.hpp"
+#include "gdrom/toc.hpp"
+
+#include "iso9660/primary_volume_descriptor.hpp"
+#include "iso9660/directory_record.hpp"
+
+void pio_data(const uint8_t * data)
+{
+  while ((gdrom::status::bsy(gdrom_if.status) | gdrom::status::drq(gdrom_if.status)) != 0);
+
+  gdrom_if.features = gdrom::features::dma::disable;
+  gdrom_if.drive_select = gdrom::drive_select::drive_select
+                        | gdrom::drive_select::lun(0);
+
+  gdrom_if.command = gdrom::command::code::packet_command;
+  while (gdrom::status::drq(gdrom_if.status) == 0);
+
+  const uint16_t * buf = reinterpret_cast<const uint16_t *>(&data[0]);
+  for (int i = 0; i < 6; i++) {
+    gdrom_if.data = buf[i];
+  }
+
+  while (gdrom::status::bsy(gdrom_if.status) != 0);
+}
+
+void read_data(uint16_t * buf, const uint32_t length)
+{
+  serial::string("read_data drq interrupt_reason: ");
+  serial::integer<uint8_t>(gdrom::status::drq(gdrom_if.status), ' ');
+  serial::integer<uint8_t>(gdrom_if.interrupt_reason);
+  for (uint32_t i = 0; i < (length / 2); i++) {
+    buf[i] = gdrom_if.data;
+  }
+}
+
+uint32_t toc__get_data_track_fad()
+{
+  auto packet = gdrom_command_packet_format::get_toc(0,     // single-density
+                                                     0x0198 // maximum toc length
+                                                     );
+  serial::string("get_toc\n");
+  pio_data(packet._data());
+
+  serial::string("byte_count: ");
+  serial::integer<uint16_t>(gdrom_if.byte_count());
+  uint16_t buf[gdrom_if.byte_count() / 2];
+  read_data(buf, gdrom_if.byte_count());
+
+  serial::string("status: ");
+  serial::integer<uint8_t>(gdrom_if.status);
+
+  auto toc = reinterpret_cast<const struct gdrom_toc::toc *>(buf);
+  for (int i = 0; i < 99; i++) {
+    if (toc->track[i].fad() == 0xffffff)
+      break;
+    serial::string("track ");
+    serial::integer<uint8_t>(i);
+    serial::integer<uint32_t>(toc->track[i].fad());
+  }
+
+  // assume track 1 is the correct track
+  return toc->track[1].fad();
+}
+
+uint32_t cd_read(uint16_t * buf,
+                 const uint32_t starting_address,
+                 const uint32_t transfer_length)
+{
+  const uint8_t data_select = 0b0010; // data
+  const uint8_t expected_data_type = 0b100; // XA mode 2 form 1
+  const uint8_t parameter_type = 0b0; // FAD specified
+  const uint8_t data = (data_select << 4) | (expected_data_type << 1) | (parameter_type << 0);
+
+  auto packet = gdrom_command_packet_format::cd_read(data,
+                                                     starting_address,
+                                                     transfer_length);
+
+  auto arst = packet._data();
+  serial::string("cd_read\n");
+  serial::string("starting_address: ");
+  serial::integer<uint32_t>(starting_address);
+  pio_data(packet._data());
+
+  uint32_t length = 0;
+  while ((gdrom::status::drq(gdrom_if.status)) != 0) {
+    const uint32_t byte_count = gdrom_if.byte_count();
+    length += byte_count;
+    read_data(buf, byte_count);
+  }
+  serial::string("status: ");
+  serial::integer<uint8_t>(gdrom_if.status);
+
+  serial::string("read length: ");
+  serial::integer<uint32_t>(length);
+  return length;
+}
+
+void main()
+{
+  // gdrom unlock undocumented register
+  g1_if.GDUNLOCK = 0x1fffff;
+
+  // Without this read from system_boot_rom, the read value of
+  // gdrom_if.status is always 0xff
+  for(uint32_t i = 0; i < 0x200000 / 4; i++) {
+    (void)system_boot_rom[i];
+  }
+
+  const uint32_t fad = toc__get_data_track_fad();
+  serial::character('\n');
+
+  const uint32_t primary_volume_descriptor = fad + 16;
+  uint16_t buf[2048 / 2];
+  const uint32_t length0 = cd_read(buf,
+                                   primary_volume_descriptor,
+                                   1 // one sector; 2048 bytes
+                                   );
+  serial::character('\n');
+
+  auto pvd = reinterpret_cast<const iso9660::primary_volume_descriptor *>(&buf[0]);
+  auto root_dr = reinterpret_cast<const iso9660::directory_record *>(&pvd->directory_record_for_root_directory[0]);
+
+  serial::string("primary volume descriptor:\n");
+  serial::string("  standard_identifier: ");
+  serial::string(pvd->standard_identifier, 5);
+  serial::character('\n');
+  serial::string("  root directory record:\n");
+  serial::string("    location of extent: ");
+  serial::integer<uint32_t>(root_dr->location_of_extent.get());
+  serial::string("    data length: ");
+  serial::integer<uint32_t>(root_dr->data_length.get());
+
+  serial::character('\n');
+
+  /*
+  for (int i = 0; i < 2048; i++) {
+    serial::hexlify(buf8[i]);
+    serial::character(' ');
+    if ((i % 16) == 15)
+      serial::character('\n');
+  }
+  */
+  serial::character('\n');
+
+  const uint32_t root_directory_extent = root_dr->location_of_extent.get();
+  const uint32_t length1 = cd_read(buf,
+                                   root_directory_extent + 150, // 150?
+                                   1 // one sector; 2048 bytes
+                                   );
+  serial::character('\n');
+
+  auto buf8 = reinterpret_cast<const uint8_t *>(buf);
+  uint32_t offset = 0;
+  while (true) {
+    serial::string("directory entry offset: ");
+    serial::integer<uint32_t>(offset);
+
+    auto dr = reinterpret_cast<const iso9660::directory_record *>(&buf8[offset]);
+    if (dr->length_of_directory_record == 0)
+      break;
+
+    serial::string("  length_of_directory_record: ");
+    serial::integer<uint8_t>(dr->length_of_directory_record);
+    serial::string("  length_of_file_identifier: ");
+    serial::integer<uint8_t>(dr->length_of_file_identifier);
+    serial::string("  file_identifier: ");
+    serial::string(dr->file_identifier, dr->length_of_file_identifier);
+    serial::character('\n');
+
+    if (dr->file_flags == 0) {
+      serial::string("  location_of_extent: ");
+      serial::integer<uint32_t>(dr->location_of_extent.get());
+      serial::string("  data_length: ");
+      serial::integer<uint32_t>(dr->data_length.get());
+
+      if (dr->file_identifier[0] != '1') {
+	const uint32_t extent = dr->location_of_extent.get();
+
+        uint16_t buf2[2048 / 2];
+        const uint32_t length1 = cd_read(buf2,
+                                         extent + 150, // 150?
+                                         1 // one sector; 2048 bytes
+                                         );
+
+	auto file = reinterpret_cast<const uint8_t *>(&buf2[0]);
+	serial::string("---begin file content---\n");
+        serial::string(file, dr->data_length.get());
+	serial::string("---end file content---\n");
+      }
+    }
+
+    offset += dr->length_of_directory_record;
+  }
+
+  serial::integer<uint32_t>(offset);
+
+  while (1);
+}
+
+/*
+  for (int i = 0; i < 12; i++) {
+    serial::hexlify(arst[i]);
+    serial::character(' ');
+  }
+  serial::character('\n');
+*/
diff --git a/example/gdrom_test.cpp b/example/gdrom_test.cpp
index c691d9a..26dc028 100644
--- a/example/gdrom_test.cpp
+++ b/example/gdrom_test.cpp
@@ -1,8 +1,9 @@
-#include "gdrom/gdrom.hpp"
-#include "gdrom/gdrom_bits.hpp"
+#include <cstdint>
+
 #include "memorymap.hpp"
 #include "systembus.hpp"
-
+#include "gdrom/gdrom.hpp"
+#include "gdrom/gdrom_bits.hpp"
 #include "sh7091/serial.hpp"
 
 void test_unit()
@@ -172,7 +173,7 @@ void get_toc()
    41 00 2f 7c (lead-out information)
 */
 
-void cd_read()
+void cd_read2()
 {
   // CD-ROM XA mode 2 form 1
 
@@ -182,7 +183,7 @@ void cd_read()
 
 
   const uint8_t data[12] = {
-    0x31, // CD_READ
+    0x31, // CD_READ2
     (data_select << 4) | (expected_data_type << 1) | (parameter_type << 0),
 
     0x00, // starting address (msb)
@@ -238,7 +239,7 @@ void main()
   req_mode();
   get_toc();
 
-  cd_read();
+  cd_read2();
 
   while (1);
 }
diff --git a/gdrom/command_packet_format_byte_order.hpp b/gdrom/command_packet_format_byte_order.hpp
index 54439ff..e57c83a 100644
--- a/gdrom/command_packet_format_byte_order.hpp
+++ b/gdrom/command_packet_format_byte_order.hpp
@@ -7,15 +7,15 @@ namespace gdrom_command_packet_format {
   template <>
   constexpr void byte_order<2>(uint8_t * buf, const uint32_t n)
   {
-    buf[0] = n >> 8;
-    buf[1] = n >> 0;
+    buf[0] = (n >> 8) & 0xff;
+    buf[1] = (n >> 0) & 0xff;
   }
 
   template <>
   constexpr void byte_order<3>(uint8_t * buf, const uint32_t n)
   {
-    buf[0] = n >> 16;
-    buf[1] = n >> 8;
-    buf[1] = n >> 0;
+    buf[0] = (n >> 16) & 0xff;
+    buf[1] = (n >> 8) & 0xff;
+    buf[2] = (n >> 0) & 0xff;
   }
 }
diff --git a/gdrom/gdrom.hpp b/gdrom/gdrom.hpp
index e2e2841..7d4292d 100644
--- a/gdrom/gdrom.hpp
+++ b/gdrom/gdrom.hpp
@@ -22,11 +22,11 @@ struct gdrom_if_reg {
     reg8  sector_count;
   };
   const reg8  _pad4[3];
-  reg8  sector_number;
+  const reg8  sector_number;
   const reg8  _pad5[3];
-  reg8  byte_control_low;
+  reg8  byte_count_low;
   const reg8  _pad6[3];
-  reg8  byte_control_high;
+  reg8  byte_count_high;
   const reg8  _pad7[3];
   reg8  drive_select;
   const reg8  _pad8[3];
@@ -34,6 +34,11 @@ struct gdrom_if_reg {
     const reg8  status;
     reg8  command;
   };
+
+  uint16_t byte_count() const
+  {
+    return (byte_count_high << 8) | (byte_count_low << 0);
+  }
 };
 
 static_assert((offsetof (struct gdrom_if_reg, alternate_status)) == 24);
@@ -44,8 +49,8 @@ static_assert((offsetof (struct gdrom_if_reg, features)) == 132);
 static_assert((offsetof (struct gdrom_if_reg, interrupt_reason)) == 136);
 static_assert((offsetof (struct gdrom_if_reg, sector_count)) == 136);
 static_assert((offsetof (struct gdrom_if_reg, sector_number)) == 140);
-static_assert((offsetof (struct gdrom_if_reg, byte_control_low)) == 144);
-static_assert((offsetof (struct gdrom_if_reg, byte_control_high)) == 148);
+static_assert((offsetof (struct gdrom_if_reg, byte_count_low)) == 144);
+static_assert((offsetof (struct gdrom_if_reg, byte_count_high)) == 148);
 static_assert((offsetof (struct gdrom_if_reg, drive_select)) == 152);
 static_assert((offsetof (struct gdrom_if_reg, status)) == 156);
 static_assert((offsetof (struct gdrom_if_reg, command)) == 156);
diff --git a/gdrom/toc.hpp b/gdrom/toc.hpp
new file mode 100644
index 0000000..03bd346
--- /dev/null
+++ b/gdrom/toc.hpp
@@ -0,0 +1,89 @@
+#include <cstdint>
+
+namespace gdrom_toc {
+
+struct track {
+  const uint8_t _control_adr;
+  const uint8_t _fad[3];
+
+  uint32_t fad() const
+  {
+    return (_fad[0] << 16) | (_fad[1] << 8) | (_fad[2] << 0);
+  }
+
+  uint8_t control() const
+  {
+    return (_control_adr >> 4) & 0xf;
+  }
+
+  uint8_t adr() const
+  {
+    return (_control_adr >> 0) & 0xf;
+  }
+};
+static_assert((sizeof (track)) == 4);
+
+struct start_track {
+  const uint8_t _control_adr;
+  const uint8_t start_track_number;
+  const uint8_t _zero[2];
+
+  uint8_t control() const
+  {
+    return (_control_adr >> 4) & 0xf;
+  }
+
+  uint8_t adr() const
+  {
+    return (_control_adr >> 0) & 0xf;
+  }
+};
+static_assert((sizeof (start_track)) == 4);
+
+struct end_track {
+  const uint8_t _control_adr;
+  const uint8_t end_track_number;
+  const uint8_t _zero[2];
+
+  uint8_t control() const
+  {
+    return (_control_adr >> 4) & 0xf;
+  }
+
+  uint8_t adr() const
+  {
+    return (_control_adr >> 0) & 0xf;
+  }
+};
+static_assert((sizeof (end_track)) == 4);
+
+struct lead_out {
+  const uint8_t _control_adr;
+  const uint8_t _fad[3];
+
+  uint32_t fad() const
+  {
+    return (_fad[0] << 16) | (_fad[1] << 8) | (_fad[2] << 0);
+  }
+
+  uint8_t control() const
+  {
+    return (_control_adr >> 4) & 0xf;
+  }
+
+  uint8_t adr() const
+  {
+    return (_control_adr >> 0) & 0xf;
+  }
+};
+static_assert((sizeof (lead_out)) == 4);
+
+struct toc {
+  struct track track[99];
+  struct start_track start_track;
+  struct end_track end_track;
+  struct lead_out lead_out;
+};
+static_assert((sizeof (toc)) == 408);
+
+}
diff --git a/iso9660/byte_position.py b/iso9660/byte_position.py
index 61fef12..8e7110b 100644
--- a/iso9660/byte_position.py
+++ b/iso9660/byte_position.py
@@ -1,6 +1,6 @@
 import sys
 from dataclasses import dataclass
-from os.path import splitext
+from os import path
 
 from csv_input import read_input
 from generate import renderer
@@ -89,6 +89,8 @@ def header():
     yield ""
 
 def render_fields(input_name, fields):
+    yield "namespace iso9660 {"
+
     yield f"struct {input_name} {{"
     for field in fields:
         field_size = (field.end - field.start) + 1
@@ -108,9 +110,12 @@ def render_fields(input_name, fields):
     for field in fields:
         yield f"static_assert((offsetof (struct {input_name}, {field.name})) == {field.start - 1});"
 
+    yield "}" # namespace
+
 if __name__ == "__main__":
     input_file = sys.argv[1]
-    input_name, _ = splitext(input_file)
+    input_name0, _ = path.splitext(input_file)
+    _, input_name = path.split(input_name0)
     rows = read_input(input_file)
     fields = list(parse(rows))
     render, out = renderer()
diff --git a/iso9660/directory_record.hpp b/iso9660/directory_record.hpp
index 63f2c7e..5b1d5c4 100644
--- a/iso9660/directory_record.hpp
+++ b/iso9660/directory_record.hpp
@@ -5,28 +5,29 @@
 
 #include "uint_le_be.hpp"
 
-struct directory_record {
-  const uint8_t length_of_directory_record;
-  const uint8_t extended_attribute_record_length;
-  const uint32_le_be location_of_extent;
-  const uint32_le_be data_length;
-  const uint8_t recording_date_and_time[7];
-  const uint8_t file_flags;
-  const uint8_t file_unit_size;
-  const uint8_t interleave_gap_size;
-  const uint16_le_be volume_sequence_number;
-  const uint8_t length_of_file_identifier;
-  const uint8_t file_identifier[];
-};
-
-static_assert((offsetof (struct directory_record, length_of_directory_ecord)) == 0);
-static_assert((offsetof (struct directory_record, extended_attribute_record_length)) == 1);
-static_assert((offsetof (struct directory_record, location_of_extent)) == 2);
-static_assert((offsetof (struct directory_record, data_length)) == 10);
-static_assert((offsetof (struct directory_record, recording_date_and_time)) == 18);
-static_assert((offsetof (struct directory_record, file_flags)) == 25);
-static_assert((offsetof (struct directory_record, file_unit_size)) == 26);
-static_assert((offsetof (struct directory_record, interleave_gap_size)) == 27);
-static_assert((offsetof (struct directory_record, volume_sequence_number)) == 28);
-static_assert((offsetof (struct directory_record, length_of_file_identifier)) == 32);
-static_assert((offsetof (struct directory_record, file_identifier)) == 33);
+namespace iso9660 {
+  struct directory_record {
+    const uint8_t length_of_directory_record;
+    const uint8_t extended_attribute_record_length;
+    const uint32_le_be location_of_extent;
+    const uint32_le_be data_length;
+    const uint8_t recording_date_and_time[7];
+    const uint8_t file_flags;
+    const uint8_t file_unit_size;
+    const uint8_t interleave_gap_size;
+    const uint16_le_be volume_sequence_number;
+    const uint8_t length_of_file_identifier;
+    const uint8_t file_identifier[];
+  };
+  static_assert((offsetof (struct directory_record, length_of_directory_record)) == 0);
+  static_assert((offsetof (struct directory_record, extended_attribute_record_length)) == 1);
+  static_assert((offsetof (struct directory_record, location_of_extent)) == 2);
+  static_assert((offsetof (struct directory_record, data_length)) == 10);
+  static_assert((offsetof (struct directory_record, recording_date_and_time)) == 18);
+  static_assert((offsetof (struct directory_record, file_flags)) == 25);
+  static_assert((offsetof (struct directory_record, file_unit_size)) == 26);
+  static_assert((offsetof (struct directory_record, interleave_gap_size)) == 27);
+  static_assert((offsetof (struct directory_record, volume_sequence_number)) == 28);
+  static_assert((offsetof (struct directory_record, length_of_file_identifier)) == 32);
+  static_assert((offsetof (struct directory_record, file_identifier)) == 33);
+}
diff --git a/iso9660/primary_volume_descriptor.hpp b/iso9660/primary_volume_descriptor.hpp
index 6aa75d6..674d7e7 100644
--- a/iso9660/primary_volume_descriptor.hpp
+++ b/iso9660/primary_volume_descriptor.hpp
@@ -5,72 +5,73 @@
 
 #include "uint_le_be.hpp"
 
-struct primary_volume_descriptor {
-  const uint8_t volume_descriptor_type;
-  const uint8_t standard_identifier[5];
-  const uint8_t volume_descriptor_version;
-  const uint8_t _res1;
-  const uint8_t system_identifier[32];
-  const uint8_t volume_identifier[32];
-  const uint8_t _res2[8];
-  const uint32_le_be volume_space_size;
-  const uint8_t _res3[32];
-  const uint16_le_be volume_set_size;
-  const uint16_le_be volume_sequence_number;
-  const uint16_le_be logical_block_size;
-  const uint32_le_be path_table_size;
-  const uint16_le_be location_of_occurrence_of_type_l_path_table;
-  const uint16_le_be location_of_optional_occurence_of_type_l_path_table;
-  const uint16_le_be location_of_occurence_of_type_m_path_table;
-  const uint16_le_be location_of_optional_occurence_of_type_m_path_table;
-  const uint8_t directory_record_for_root_directory[34];
-  const uint8_t volume_set_identifier[128];
-  const uint8_t publisher_identifier[128];
-  const uint8_t data_preparer_identifier[128];
-  const uint8_t application_identifier[128];
-  const uint8_t copyright_file_identifier[37];
-  const uint8_t abstract_file_identifier[37];
-  const uint8_t bibliographic_file_identifier[37];
-  const uint8_t volume_creation_date_and_time[17];
-  const uint8_t volume_modification_date_and_time[17];
-  const uint8_t volume_expiration_date_and_time[17];
-  const uint8_t volume_effective_date_and_time[17];
-  const uint8_t file_structure_version;
-  const uint8_t _res4;
-  const uint8_t application_use[512];
-  const uint8_t _res5[653];
-};
-
-static_assert((offsetof (struct primary_volume_descriptor, volume_descriptor_type)) == 0);
-static_assert((offsetof (struct primary_volume_descriptor, standard_identifier)) == 1);
-static_assert((offsetof (struct primary_volume_descriptor, volume_descriptor_version)) == 6);
-static_assert((offsetof (struct primary_volume_descriptor, _res1)) == 7);
-static_assert((offsetof (struct primary_volume_descriptor, system_identifier)) == 8);
-static_assert((offsetof (struct primary_volume_descriptor, volume_identifier)) == 40);
-static_assert((offsetof (struct primary_volume_descriptor, _res2)) == 72);
-static_assert((offsetof (struct primary_volume_descriptor, volume_space_size)) == 80);
-static_assert((offsetof (struct primary_volume_descriptor, _res3)) == 88);
-static_assert((offsetof (struct primary_volume_descriptor, volume_set_size)) == 120);
-static_assert((offsetof (struct primary_volume_descriptor, volume_sequence_number)) == 124);
-static_assert((offsetof (struct primary_volume_descriptor, logical_block_size)) == 128);
-static_assert((offsetof (struct primary_volume_descriptor, path_table_size)) == 132);
-static_assert((offsetof (struct primary_volume_descriptor, location_of_occurrence_of_type_l_path_table)) == 140);
-static_assert((offsetof (struct primary_volume_descriptor, location_of_optional_occurence_of_type_l_path_table)) == 144);
-static_assert((offsetof (struct primary_volume_descriptor, location_of_occurence_of_type_m_path_table)) == 148);
-static_assert((offsetof (struct primary_volume_descriptor, location_of_optional_occurence_of_type_m_path_table)) == 152);
-static_assert((offsetof (struct primary_volume_descriptor, directory_record_for_root_directory)) == 156);
-static_assert((offsetof (struct primary_volume_descriptor, volume_set_identifier)) == 190);
-static_assert((offsetof (struct primary_volume_descriptor, publisher_identifier)) == 318);
-static_assert((offsetof (struct primary_volume_descriptor, data_preparer_identifier)) == 446);
-static_assert((offsetof (struct primary_volume_descriptor, application_identifier)) == 574);
-static_assert((offsetof (struct primary_volume_descriptor, copyright_file_identifier)) == 702);
-static_assert((offsetof (struct primary_volume_descriptor, abstract_file_identifier)) == 739);
-static_assert((offsetof (struct primary_volume_descriptor, bibliographic_file_identifier)) == 776);
-static_assert((offsetof (struct primary_volume_descriptor, volume_creation_date_and_time)) == 813);
-static_assert((offsetof (struct primary_volume_descriptor, volume_modification_date_and_time)) == 830);
-static_assert((offsetof (struct primary_volume_descriptor, volume_expiration_date_and_time)) == 847);
-static_assert((offsetof (struct primary_volume_descriptor, volume_effective_date_and_time)) == 864);
-static_assert((offsetof (struct primary_volume_descriptor, file_structure_version)) == 881);
-static_assert((offsetof (struct primary_volume_descriptor, _res4)) == 882);
-static_assert((offsetof (struct primary_volume_descriptor, application_use)) == 883);
-static_assert((offsetof (struct primary_volume_descriptor, _res5)) == 1395);
+namespace iso9660 {
+  struct primary_volume_descriptor {
+    const uint8_t volume_descriptor_type;
+    const uint8_t standard_identifier[5];
+    const uint8_t volume_descriptor_version;
+    const uint8_t _res1;
+    const uint8_t system_identifier[32];
+    const uint8_t volume_identifier[32];
+    const uint8_t _res2[8];
+    const uint32_le_be volume_space_size;
+    const uint8_t _res3[32];
+    const uint16_le_be volume_set_size;
+    const uint16_le_be volume_sequence_number;
+    const uint16_le_be logical_block_size;
+    const uint32_le_be path_table_size;
+    const uint16_le_be location_of_occurrence_of_type_l_path_table;
+    const uint16_le_be location_of_optional_occurence_of_type_l_path_table;
+    const uint16_le_be location_of_occurence_of_type_m_path_table;
+    const uint16_le_be location_of_optional_occurence_of_type_m_path_table;
+    const uint8_t directory_record_for_root_directory[34];
+    const uint8_t volume_set_identifier[128];
+    const uint8_t publisher_identifier[128];
+    const uint8_t data_preparer_identifier[128];
+    const uint8_t application_identifier[128];
+    const uint8_t copyright_file_identifier[37];
+    const uint8_t abstract_file_identifier[37];
+    const uint8_t bibliographic_file_identifier[37];
+    const uint8_t volume_creation_date_and_time[17];
+    const uint8_t volume_modification_date_and_time[17];
+    const uint8_t volume_expiration_date_and_time[17];
+    const uint8_t volume_effective_date_and_time[17];
+    const uint8_t file_structure_version;
+    const uint8_t _res4;
+    const uint8_t application_use[512];
+    const uint8_t _res5[653];
+  };
+  static_assert((offsetof (struct primary_volume_descriptor, volume_descriptor_type)) == 0);
+  static_assert((offsetof (struct primary_volume_descriptor, standard_identifier)) == 1);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_descriptor_version)) == 6);
+  static_assert((offsetof (struct primary_volume_descriptor, _res1)) == 7);
+  static_assert((offsetof (struct primary_volume_descriptor, system_identifier)) == 8);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_identifier)) == 40);
+  static_assert((offsetof (struct primary_volume_descriptor, _res2)) == 72);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_space_size)) == 80);
+  static_assert((offsetof (struct primary_volume_descriptor, _res3)) == 88);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_set_size)) == 120);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_sequence_number)) == 124);
+  static_assert((offsetof (struct primary_volume_descriptor, logical_block_size)) == 128);
+  static_assert((offsetof (struct primary_volume_descriptor, path_table_size)) == 132);
+  static_assert((offsetof (struct primary_volume_descriptor, location_of_occurrence_of_type_l_path_table)) == 140);
+  static_assert((offsetof (struct primary_volume_descriptor, location_of_optional_occurence_of_type_l_path_table)) == 144);
+  static_assert((offsetof (struct primary_volume_descriptor, location_of_occurence_of_type_m_path_table)) == 148);
+  static_assert((offsetof (struct primary_volume_descriptor, location_of_optional_occurence_of_type_m_path_table)) == 152);
+  static_assert((offsetof (struct primary_volume_descriptor, directory_record_for_root_directory)) == 156);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_set_identifier)) == 190);
+  static_assert((offsetof (struct primary_volume_descriptor, publisher_identifier)) == 318);
+  static_assert((offsetof (struct primary_volume_descriptor, data_preparer_identifier)) == 446);
+  static_assert((offsetof (struct primary_volume_descriptor, application_identifier)) == 574);
+  static_assert((offsetof (struct primary_volume_descriptor, copyright_file_identifier)) == 702);
+  static_assert((offsetof (struct primary_volume_descriptor, abstract_file_identifier)) == 739);
+  static_assert((offsetof (struct primary_volume_descriptor, bibliographic_file_identifier)) == 776);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_creation_date_and_time)) == 813);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_modification_date_and_time)) == 830);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_expiration_date_and_time)) == 847);
+  static_assert((offsetof (struct primary_volume_descriptor, volume_effective_date_and_time)) == 864);
+  static_assert((offsetof (struct primary_volume_descriptor, file_structure_version)) == 881);
+  static_assert((offsetof (struct primary_volume_descriptor, _res4)) == 882);
+  static_assert((offsetof (struct primary_volume_descriptor, application_use)) == 883);
+  static_assert((offsetof (struct primary_volume_descriptor, _res5)) == 1395);
+}
diff --git a/iso9660/uint_le_be.hpp b/iso9660/uint_le_be.hpp
index 1e6ded3..5fcf80d 100644
--- a/iso9660/uint_le_be.hpp
+++ b/iso9660/uint_le_be.hpp
@@ -2,7 +2,6 @@
 
 #include <cstdint>
 #include <bit>
-#include <iostream>
 
 template <typename T>
 struct uint_le_be {
diff --git a/regs/gdrom.csv b/regs/gdrom.csv
index cc834f3..636fa7e 100644
--- a/regs/gdrom.csv
+++ b/regs/gdrom.csv
@@ -6,9 +6,9 @@
 "0084","1","features","W",
 "0088","1","interrupt_reason","R",
 "0088","1","sector_count","W",
-"008C","1","sector_number","RW",
-"0090","1","byte_control_low","RW",
-"0094","1","byte_control_high","RW",
+"008C","1","sector_number","R",
+"0090","1","byte_count_low","RW",
+"0094","1","byte_count_high","RW",
 "0098","1","drive_select","RW",
 "009C","1","status","R",
 "009C","1","command","W",
diff --git a/regs/gdrom.ods b/regs/gdrom.ods
index 434c1e1..f6f6647 100644
Binary files a/regs/gdrom.ods and b/regs/gdrom.ods differ
diff --git a/regs/gen/gdrom.py b/regs/gen/gdrom.py
index b9cbca0..4d80478 100644
--- a/regs/gen/gdrom.py
+++ b/regs/gen/gdrom.py
@@ -40,6 +40,12 @@ def group_by_address(rows):
 
     return list(sorted(_groups.items(), key=lambda kv: kv[0]))
 
+def byte_count():
+    yield "uint16_t byte_count() const"
+    yield "{"
+    yield "return (byte_count_high << 8) | (byte_count_low << 0);"
+    yield "}"
+
 def render_groups(groups):
     next_address = 0
     reserved_num = 0
@@ -67,6 +73,9 @@ def render_groups(groups):
 
         next_address = address + group[0].size
 
+    yield ""
+    yield from byte_count()
+
     yield "};"
 
 
diff --git a/sh7091/serial.cpp b/sh7091/serial.cpp
index 2d4c611..b2d8032 100644
--- a/sh7091/serial.cpp
+++ b/sh7091/serial.cpp
@@ -47,6 +47,14 @@ void string(const char * s)
   }
 }
 
+void string(const uint8_t * s, uint32_t len)
+{
+  while (len > 0) {
+    character(*s++);
+    len--;
+  }
+}
+
 void hexlify(const uint8_t n)
 {
   constexpr uint32_t length = 2;
diff --git a/sh7091/serial.hpp b/sh7091/serial.hpp
index 27a9ad8..9450830 100644
--- a/sh7091/serial.hpp
+++ b/sh7091/serial.hpp
@@ -6,6 +6,8 @@ void character(const char c);
 
 void string(const char * s);
 
+void string(const uint8_t * s, uint32_t len);
+
 void hexlify(const uint8_t n);
 
 template <typename T>