*************************************************************************
*                                                                       *
*       OSBYTE 154 (&9A) SET VIDEO ULA                                  *
*                                                                       *
*************************************************************************

E9FF	TXA         ;osbyte entry! X transferred to A thence to

*******Set Video ULA control register **entry from VDU routines **************
    	            ;called from &CBA6, &DD37

EA00	PHP         ;save flags
EA01	SEI         ;disable interupts
EA02	STA &0248   ;save RAM copy of new parameter
EA05	STA &FE20   ;write to control register
EA08	LDA &0253   ;read  space count
EA0B	STA &0251   ;set flash counter to this value
EA0E	PLP         ;get back status
EA0F	RTS         ;and return


*************************************************************************
*                                                                       *
*        OSBYTE &9B (155) write to palette register                     *
*                                                                       *
*************************************************************************

    	    ;entry X contains value to write
EA10	TXA         ;A=X
EA11	EOR #&07    ;convert to palette format
EA13	PHP         ;
EA14	SEI         ;prevent interrupts
EA15	STA &0249   ;store as current palette setting
EA18	STA &FE21   ;store actual colour in register
EA1B	PLP         ;get back flags
EA1C	RTS         ;and exit
    	            ;


*************************************************************************
*       GSINIT  string initialisation                                   *
*       F2/3 points to string offset by Y                               *
*                                                                       *
*       ON EXIT                                                         *
*       Z flag set indicates null string,                               *
*       Y points to first non blank character                           *
*       A contains first non blank character                            *
*************************************************************************

EA1D	CLC         ;clear carry

EA1E	ROR &E4     ;Rotate moves carry to &E4
EA20	JSR &E03A   ;get character from text
EA23	INY         ;increment Y to point at next character
EA24	CMP #&22    ;check to see if its '"'
EA26	BEQ &EA2A   ;if so EA2A (carry set)
EA28	DEY         ;decrement Y
EA29	CLC         ;clear carry
EA2A	ROR &E4     ;move bit 7 to bit 6 and put carry in bit 7
EA2C	CMP #&0D    ;check to see if its CR to set Z
EA2E	RTS         ;and return


*************************************************************************
*       GSREAD  string read routine                                     *
*       F2/3 points to string offset by Y                               *
*                                                                       *
*************************************************************************
    	            ;
EA2F	LDA #&00    ;A=0
EA31	STA &E5     ;store A
EA33	LDA (&F2),Y ;read first character
EA35	CMP #&0D    ;is it CR
EA37	BNE &EA3F   ;if not goto EA3F
EA39	BIT &E4     ;if bit 7=1 no 2nd '"' found
EA3B	BMI &EA8F   ;goto EA8F
EA3D	BPL &EA5A   ;if not EA5A

EA3F	CMP #&20    ;is less than a space?
EA41	BCC &EA8F   ;goto EA8F
EA43	BNE &EA4B   ;if its not a space EA4B
EA45	BIT &E4     ;is bit 7 of &E4 =1
EA47	BMI &EA89   ;if so goto EA89
EA49	BVC &EA5A   ;if bit 6 = 0 EA5A
EA4B	CMP #&22    ;is it '"'
EA4D	BNE &EA5F   ;if not EA5F
EA4F	BIT &E4     ;if so and Bit 7 of &E4 =0 (no previous ")
EA51	BPL &EA89   ;then EA89
EA53	INY         ;else point at next character
EA54	LDA (&F2),Y ;get it
EA56	CMP #&22    ;is it '"'
EA58	BEQ &EA89   ;if so then EA89

EA5A	JSR &E03A   ;read a byte from text
EA5D	SEC         ;and return with
EA5E	RTS         ;carry set
    	            ;
EA5F	CMP #&7C    ;is it '|'
EA61	BNE &EA89   ;if not EA89
EA63	INY         ;if so increase Y to point to next character
EA64	LDA (&F2),Y ;get it
EA66	CMP #&7C    ;and compare it with '|' again
EA68	BEQ &EA89   ;if its '|' then EA89
EA6A	CMP #&22    ;else is it '"'
EA6C	BEQ &EA89   ;if so then EA89
EA6E	CMP #&21    ;is it !
EA70	BNE &EA77   ;if not then EA77
EA72	INY         ;increment Y again
EA73	LDA #&80    ;set bit 7
EA75	BNE &EA31   ;loop back to EA31 to set bit 7 in next CHR
EA77	CMP #&20    ;is it a space
EA79	BCC &EA8F   ;if less than EA8F Bad String Error
EA7B	CMP #&3F    ;is it '?'
EA7D	BEQ &EA87   ;if so EA87
EA7F	JSR &EABF   ;else modify code as if CTRL had been pressed
EA82	BIT &D9B7   ;if bit 6 set
EA85	BVS &EA8A   ;then EA8A
EA87	LDA #&7F    ;else set bits 0 to 6 in A

EA89	CLV         ;clear V
EA8A	INY         ;increment Y
EA8B	ORA &E5     ;
EA8D	CLC         ;clear carry
EA8E	RTS         ;Return
    	            ;
EA8F	BRK         ;
EA90	DB  &FD     ;error number
EA93	DB 'Bad String' ; message
EA9B	BRK         ;


************ Modify code as if SHIFT pressed *****************************

EA9C	CMP #&30    ;if A='0' skip routine
EA9E	BEQ &EABE   ;
EAA0	CMP #&40    ;if A='@' skip routine
EAA2	BEQ &EABE   ;
EAA4	BCC &EAB8   ;if A<'@' then EAB8
EAA6	CMP #&7F    ;else is it DELETE

EAA8	BEQ &EABE   ;if so skip routine
EAAA	BCS &EABC   ;if greater than &7F then toggle bit 4
EAAC	EOR #&30    ;reverse bits 4 and 5
EAAE	CMP #&6F    ;is it &6F (previously ' _' (&5F))
EAB0	BEQ &EAB6   ;goto EAB6
EAB2	CMP #&50    ;is it &50 (previously '`' (&60))
EAB4	BNE &EAB8   ;if not EAB8
EAB6	EOR #&1F    ;else continue to convert ` _
EAB8	CMP #&21    ;compare &21 '!'
EABA	BCC &EABE   ;if less than return
EABC	EOR #&10    ;else finish conversion by toggling bit 4
EABE	RTS         ;exit
    	            ;
    	            ;ASCII codes &00 &20 no change
    	            ;21-3F have bit 4 reverses (31-3F)
    	            ;41-5E A-Z have bit 5 reversed a-z
    	            ;5F & 60 are reversed
    	            ;61-7E bit 5 reversed a-z becomes A-Z
    	            ;DELETE unchanged
    	            ;&80+ has bit 4 changed


************** Implement CTRL codes *************************************


EABF	CMP #&7F    ;is it DEL
EAC1	BEQ &EAD1   ;if so ignore routine
EAC3	BCS &EAAC   ;if greater than &7F go to EAAC
EAC5	CMP #&60    ;if A<>'`'
EAC7	BNE &EACB   ;goto EACB
EAC9	LDA #&5F    ;if A=&60, A=&5F

EACB	CMP #&40    ;if A<&40
EACD	BCC &EAD1   ;goto EAD1  and return unchanged
EACF	AND #&1F    ;else zero bits 5 to 7
EAD1	RTS         ;return
    	            ;
EAD2	DB  '/!BOOT',&0D