Volex TTX2000 S Issue 1.2: Routine at 1163

1163: select_channel: Channel selection and tuning display.

Used by the routine at handle_keypress.
select_channel	1163	CALL clear_page_number	Clear page number display.
	1166	CALL display_header_row	Decode and display header row data.
	1169	LD A,(control_register)	Clear bit 2 of control_register and output to control register to disable AFC.
	116C	AND $FB
	116E	LD (control_register),A
	1171	OUT ($7F),A
select_channel_0	1173	CALL detect_any_key	Detect if any key is pressed.
	1176	AND A	If a key is pressed, jump to select_channel_1.
	1177	JR NZ,select_channel_1	If a key is pressed, jump to select_channel_1.
	1179	PUSH HL	Write 'C' to first byte of page display buffer.
	117A	LD HL,(page_display_buffer_pointer)
	117D	LD (HL),$43
	117F	POP HL
	1180	CALL data_to_header_row	Call data_to_header_row to copy header row from page receive buffer into page display buffer.
	1183	CALL display_header_row	Decode and display header row data.
	1186	JR select_channel_0	Loop until a key is pressed.
select_channel_1	1188	CALL get_dec_digit	Call get_dec_digit to get a keypress in the range 0-9.
	118B	CP $35	Loop until key code is greater than or equal to $31 and less than $35 ('1' to '4').
	118D	JR NC,select_channel_0
	118F	CP $31
	1191	JR C,select_channel_0
	1193	PUSH HL	Write key code to second byte of page display buffer.
	1194	LD HL,(page_display_buffer_pointer)
	1197	INC HL
	1198	LD (HL),A
	1199	POP HL
	119A	DEC A	Subtract 1 from key code and convert to integer in range 0-3.
	119B	AND $03
	119D	LD (control_register),A	Store result in control_register and output to control register to set channel.
	11A0	OUT ($7F),A
	11A2	CALL display_header_row	Decode and display header row data.
	11A5	LD BC,$FFFF	Loop to delay for approximately half a second.
select_channel_2	11A8	DEC BC
	11A9	LD A,B
	11AA	AND A
	11AB	JR NZ,select_channel_2
	11AD	LD A,(control_register)	Set bit 2 of control_register and output to control register to reenable AFC.
	11B0	OR $04
	11B2	LD (control_register),A
	11B5	OUT ($7F),A
	11B7	CALL restore_number	Restore page number from number_display_buffer.
	11BA	CALL clear_receive_rows	Clear all rows except header in page receive buffer.
	11BD	CALL clear_page_buffer	Clear page display buffer.
	11C0	CALL decode_page	Call decode_page and return.
	11C3	RET	Call decode_page and return.