Volex TTX2000 S Issue 1.2: Memory map

Page	Byte	Address	Description
0	0	0000	START: ROM reset
0	4	0004	Unused
0	10	000A	ignore_subcode: Prepare to execute page_found.
0	18	0012	inhibit_display_clear: Clear inhibit_display and set exit_pointer to backup_exit_pointer.
0	31	001F	Unused
0	56	0038	MASK_INT: IM 1 maskable interrupt service routine
0	66	0042	Unused
0	102	0066	NMI: Non-Maskable interrupt vector
0	105	0069	NMI_ISR: Non-Maskable Interrupt service routine
2	122	027A	Unused
2	128	0280	hamming_decode_hl: Hamming 8/4 decode the byte at address in HL and return it in B.
2	139	028B	set_hardware_counter: Reads a byte from the decoder's SRAM but doesn't retain it. This sets an internal 4 bit counter to bits 6-9 of the read address.
2	146	0292	decode_magazine_number: Get the magazine number from the Magazine Row Address Group.
2	157	029D	decode_packet_number: Get the packet address from the Magazine Row Address Group.
2	183	02B7	store_packet_30: Copy packet to row 29 of page receive buffer.
2	202	02CA	init_memory: Main initialization routine.
3	40	0328	init_variables: Initialize BASIC system variables in a similar way to the BASIC ROM 'NEW' routine and initialize own variables in printer buffer.
4	58	043A	NMI_VECTOR: Jump to NMI service routine (Copied to NMI_JUMP).
4	61	043D	init_48k: Initialise pointers for 48k systems.
4	81	0451	48k_pointer_table.
4	109	046D	init_16k: Initialise pointers for 16k systems
4	129	0481	16k_pointer_table.
4	157	049D	initial_CHINFO: BASIC channel information initialization data.
4	178	04B2	initial_STRMS: BASIC stream addresses initialization data.
4	192	04C0	menu_data: Main menu page data (with teletext control codes).
6	64	0640	display_menu: Display the main menu and wait for enter key to be pressed.
6	166	06A6	print_character: Print character to the screen
7	59	073B	print_half_row: Print 4 pixel rows of character bitmap over 8 pixel rows of screen (double height).
7	76	074C	print_double_column_0: Write 4 pixel rows of double height character data over 8 pixel rows at column that is a multiple of 4.
7	102	0766	print_double_column_1: Write 4 pixel rows of double height character data over 8 pixel rows at column that is 1 greater than a multiple of 4.
7	128	0780	print_double_column_2: Write 4 pixel rows of double height character data over 8 pixel rows at column that is 2 greater than a multiple of 4.
7	154	079A	print_double_column_3: Write 4 pixel rows of double height character data over 8 pixel rows at column that is 3 greater than a multiple of 4.
7	180	07B4	print_normal: Print 8 pixel rows of font data (a normal height character).
7	197	07C5	print_column_0: Write character data at column that is a multiple of 4.
7	211	07D3	print_column_1: Write character data at column that is 1 greater than a multiple of 4.
7	242	07F2	print_column_2: Write character data at column that is 2 greater than a multiple of 4.
8	15	080F	print_column_3: Write character data at column that is 3 greater than a multiple of 4.
8	27	081B	screen_address: Calculate the address in screen RAM of the second byte of character row in A.
8	77	084D	set_attrs: Set screen attributes corresponding to screen address in character screen address variable to value in temp_attr.
8	176	08B0	clear_screen: Clear display bitmap and attributes.
8	196	08C4	clear_page_buffer: Clear page display buffer to spaces.
8	223	08DF	clear_receive_rows: Clear all rows except header in page receive buffer.
8	247	08F7	decode_row: Decode row of teletext data and render it to the screen.
9	152	0998	alpha_colour_code: Alphanumeric colour control code.
9	170	09AA	normal_code: Handle normal size control code.
9	182	09B6	double_code: Handle double height control code.
9	201	09C9	mosaics_colour_code: Handle a mosaics colour code.
9	235	09EB	conceal_code: Handle conceal code.
9	251	09FB	contiguous_code: Handle contiguous mosaics cotrol code.
10	2	0A02	separated_code: Handle separated mosaics cotrol code.
10	23	0A17	black_background_code: Clear paper colour bits of temp_attr.
10	34	0A22	new_background_code: Copy ink colour bits of temp_attr to paper colour bits.
10	55	0A37	hold_mosaics_code: Handle hold mosaics code.
10	76	0A4C	Release_mosaics_code: Handle release mosaics code.
10	82	0A52	code_set_at: Display character.
10	184	0AB8	translate_colour: Translate an alphanumeric colour code to spectrum attribute colour.
10	212	0AD4	colour_translation_table.
10	220	0ADC	set_character_pointer: Set character_pointer to start of current row in page display buffer.
10	250	0AFA	wait_and_decode_page: Wait for page_ready_flag, and check for key presses.
11	70	0B46	decode_page: Decode and render 24 rows.
11	96	0B60	font_data: Alphanumeric character set font data.
14	96	0E60	init_mosaics: Initialize font data for contiguous and separated mosaic character sets.
14	201	0EC9	generate_mosaics: Generate font data for contiguous mosaic with the character code in B at the address in HL.
14	253	0EFD	copy_blast_through: Copy blast through alphanumerics font data.
15	6	0F06	Copy 32 contiguous mosaic characters from address in HL to address in DE, separating the columns.
15	17	0F11	write_top_sixels: Write bitmap in D to three rows of font data.
15	24	0F18	set_right_bits: Set right half of mosaic bits.
15	31	0F1F	get_keypress.
15	52	0F34	scan_keyboard: Loop through keyboard rows to detect a keypress and return return key code.
15	122	0F7A	keyboard_lookup_table: Mapping between spectrum keyboard port read and keycode.
15	162	0FA2	detect_any_key: Detect if any key is pressed.
15	178	0FB2	handle_keypress: Handle a keypress while in teletext mode.
15	251	0FFB	toggle_bright: Toggle bright flag.
16	9	1009	exit_routine: Relocatable exit to BASIC routine.
16	52	1034	no_printer: Break out of printer loop gracefully.
16	56	1038	print: Printer routine for Sinclair ZX Printer or Alphacom 32.
16	156	109C	enter_page: Get valid page number and display digits in row 0.
16	235	10EB	enter_page_and_clear: Get valid page number then clear the page buffer.
16	240	10F0	enter_subcode_and_clear: Get valid page subcode then clear the page buffer.
17	85	1155	get_dec_digit: Wait for a keypress in the range 0-9.
17	99	1163	select_channel: Channel selection and tuning display.
17	196	11C4	hold_indicator: Page hold string.
17	200	11C8	hold_page: Pressed H to hold page.
18	32	1220	toggle_reveal.
18	43	122B	data_to_header_row: Copy header row data from recieve buffer to page display buffer.
18	67	1243	display_header_row: Decode and display the header row.
18	87	1257	copy_page_data: Copy received page data into page display buffer.
18	119	1277	clear_page_number: Copy page number display to number_display_buffer and clear to spaces.
18	147	1293	restore_number: Copy number_display_buffer into page number display.
18	166	12A6	pagename_string: String which gets copied to RAM_pagename_string.
18	177	12B1	save_routine: Relocatable save page routine.
19	146	1392	Unused
19	148	1394	save_instruction: BASIC save instruction string.
19	180	13B4	init_hamming_table: Create 256 byte look up table of Hamming 8/4 decoded bytes.
20	129	1481	store_hamming_nibble: Read the four data bits from hamming coded byte into address in HL
20	162	14A2	hamming_error_bits_table: Values to XOR with byte to correct hamming errors.
20	170	14AA	store_hamming_error
20	174	14AE	correct_and_store_nibble: Correct a single bit error at bit position in C.
20	187	14BB	warm_start_routine: Relocatable "warm start" from BASIC routine.
20	213	14D5	clear_header: Clear page header to spaces.
20	240	14F0	copy string in HL to page header
21	18	1512	pause_3s: Pause for 3 seconds
21	28	151C	get_hex_digit: Wait for a keypress in the range 0-9 or A-F.
21	50	1532	download_complete: All telesoftware blocks downloaded.
21	56	1538	parse_download: Determine what to do with telesoftware download based on the footer.
21	130	1582	execute_basic_stop: Setup VARS, and E-LINE and prepare to execute STOP.
21	162	15A2	execute_basic_continue: Setup VARS, E-LINE, and OLDPPC, and prepare to execute CONTINUE.
21	205	15CD	setup_vars_eline: setup VARS and E-LINE.
21	233	15E9	execute_code: Relocate and execute jump to machine code routine.
21	247	15F7	page_out_to_code: Relocatable page out ROM and execute machine code routine.
21	255	15FF	Unused
22	0	1600	return_to_STOP: Prepare to execute STOP with no variables.
22	25	1619	load_next_nibbles: Load next four low nibbles into address in HL.
22	35	1623	execute_basic: Relocate and execute initialize BASIC routine.
22	50	1632	page_out_to_basic: Relocatable initialize BASIC routine.
22	209	16D1	Unused
24	90	185A	check_page: Telesoftware page checksum.
24	237	18ED	download_data: Download data from page into memory specified in nibbles at row 23, column 8.
25	56	1938	block_downloaded: See if there are undownloaded blocks remaining.
25	84	1954	load_nibbles: Read low nibble of four bytes from address in DE to word at address in HL.
25	102	1966	write_header_message: Copy up to 16 bytes from address in DE to row 0 in page display buffer.
25	125	197D	Unused
27	138	1B8A	wait_for_page: Wait up to 2 minutes for page to load (or enter key pressed).
27	189	1BBD	clear_header_start: Clear 16 characters of header to spaces.
27	216	1BD8	start_telesoftware: Load the telesoftware index on Channel 4 page 460.
28	17	1C11	Unused
28	31	1C1F	telesoftware_jump.
28	34	1C22	telesoftware_main: Main telesoftware interface loop.
28	134	1C86	display_message: Display telesoftware error and prompt for input.
28	155	1C9B	Telesoftware downloader messages.
29	21	1D15	check_footer: Check row 23 of recieved page for telesoftware footer.
29	102	1D66	buffers_in_screen: Reposition the page receive buffer at $4840 and the page display buffer at $5000 (within screen RAM).
29	157	1D9D	border_flash: Flash border to colour in A for 300ms.
29	171	1DAB	Unused
31	141	1F8D	get_hex: Get a hexadecimal keypress.
31	152	1F98	telesoftware_number: Input page number for telesoftware page search.
31	231	1FE7	Unused
31	238	1FEE	ROM authors message.
32	0	2000	decoder_RAM: Packet buffer in decoder RAM
91	0	5B00	temp_attr
91	1	5B01	save_return_pointer
91	3	5B03	char_addr
91	7	5B07	mosaics_flag
91	8	5B08	separated_mosaics_flag
91	9	5B09	double_height_flag
91	10	5B0A	row_has_double_flag
91	11	5B0B	column_offset
91	12	5B0C	character_code
91	13	5B0D	character_pointer
91	15	5B0F	hold_mosaic_character
91	16	5B10	skip_next_row_flag
91	17	5B11	row_number
91	18	5B12	hold_mosaics_flag
91	19	5B13	ignore_packets_flag
91	20	5B14	page_found_flag
91	21	5B15	packet_data_pointer
91	23	5B17	magazine_number
91	24	5B18	page_tens
91	25	5B19	page_units
91	26	5B1A	control_register
91	27	5B1B	bright_attr
91	28	5B1C	current_attr_address
91	30	5B1E	page_ready_flag
91	31	5B1F	held_separated_flag
91	32	5B20	conceal_flag
91	33	5B21	reveal_flag
91	34	5B22	number_display_buffer
91	42	5B2A	parity_flags
91	46	5B2E	hamming_table_counter
91	47	5B2F	input_buffer
91	58	5B3A	inhibit_display
91	59	5B3B	disable_rolling_headers
91	60	5B3C	interrupt_reset_flag
91	61	5B3D	backup_exit_pointer
91	63	5B3F	RAM_pagename_string
91	80	5B50	NMI_JUMP
91	83	5B53	colour_attr
91	85	5B55	field_header_flag
91	86	5B56	subpage_search_flag
91	87	5B57	subcode_digits
91	97	5B61	counter_reset_address
91	109	5B6D	page_display_buffer_pointer
91	111	5B6F	page_receive_buffer_pointer
91	113	5B71	mosaics_font_pointer
91	115	5B73	hamming_decode_table_pointer
91	117	5B75	contiguous_blast_through
91	119	5B77	separated_blast_through
91	121	5B79	warm_start_pointer
91	123	5B7B	exit_pointer
91	125	5B7D	save_page_pointer
91	127	5B7F	download_pointer
91	129	5B81	checksum_nibbles
91	131	5B83	blocks_remaining
91	133	5B85	number_of_blocks
91	137	5B89	footer_buffer
91	165	5BA5	prog_length
91	167	5BA7	vars_length
91	169	5BA9	command_length
91	171	5BAB	start_address
91	204	5BCC	warm_start_vector
91	213	5BD5	telesoftware_pointer
91	215	5BD7	print_pointer
91	217	5BD9	temporary_stack
91	253	5BFD	telesoftware_RAMT