Volex TTX2000 S Issue 1.2: Routine at 02CA

02CA: init_memory: Main initialization routine.

Used by the routine at START.
init_memory	02CA	LD DE,NMI_JUMP	Copy NMI_VECTOR to NMI_JUMP.
	02CD	LD HL,NMI_VECTOR
	02D0	LD BC,$0003
	02D3	LDIR
	02D5	LD A,$01	Set ignore_packets_flag.
	02D7	LD (ignore_packets_flag),A	Set ignore_packets_flag.
	02DA	DEC A	Clear field_header_flag and inhibit_display flag.
	02DB	LD (field_header_flag),A
	02DE	LD (inhibit_display),A
	02E1	LD HL,telesoftware_jump	Set telesoftware_pointer to telesoftware_jump. This address is different in the OEL Issue 2.3 ROM.
	02E4	LD (telesoftware_pointer),HL
	02E7	LD HL,$2240	Set counter_reset_address to $2240. This causes the gate array to only store the first 12 teletext lines of the VBI.
	02EA	LD (counter_reset_address),HL
	02ED	LD HL,print	Set print_pointer to print.
	02F0	LD (print_pointer),HL	Set print_pointer to print.
	02F3	LD SP,$7D00	Relocate stack to $7D00.
	02F6	LD A,$3F	Set I register to $3F.
	02F8	LD I,A	Set I register to $3F.
	02FA	LD A,$04	Wait 24 t-states and output $04 to control register and store in control_register. (sets channel 1 and enables automatic frequency control).
	02FC	NOP
	02FD	NOP
	02FE	NOP
	02FF	NOP
	0300	NOP
	0301	NOP
	0302	OUT ($7F),A
	0304	LD (control_register),A
	0307	LD HL,$5C00	Clear from VARS to end of memory.
	030A	LD DE,$5C01
	030D	LD BC,$A3FE
	0310	LD (HL),$00
	0312	LDIR
	0314	LD HL,$FFFF	write $55 at address $FFFF and read it back.
	0317	LD A,$55
	0319	LD (HL),A
	031A	CP (HL)
	031B	JR NZ,init_memory_0	If result matches, invert the bits and repeat the test.
	031D	CPL
	031E	LD (HL),A
	031F	CP (HL)
	0320	JR NZ,init_memory_0	If result matches again jump to init_48k to setup pointers for 48k available memory.
	0322	JP init_48k
init_memory_0	0325	JP init_16k	If either test failed, jump to init_16k to set up pointers for 16k available memory.