The printer routines
THE 'COPY SCREEN' ROUTINE
This routine has two entry points. The first one, #161E, is used with the BASIC
commands 'SAVE/LOAD/VERIFY/MERGE SCREEN$'. The second entry point (#1621) is used for
the 'COPY' command itself. Depending on the parameter following the 'SCREEN$', the
normal or the grey scale screen dump is used.
161E DUMP_SCR$ POP HL Drop the return address (within the
routine which called 'EXPT_PARMS').
161F JR #1627,COPY_1 Jump forward.
1621 COPY RST #28,NEXT_C_RAM Advance CH_ADD.
1622 CP 170 Give 'Nonsense in GDOS' error if
1624 JP NZ,#2920,REP_0 command isn't followed by 'SCREEN$'.
1627 COPY_1 LD A,"1" Default is '1' for 'normal' dump.
1629 LD (#1E00),A
162C RST #28,NEXT_C_RAM Advance CH_ADD
162D CP 13
162F JR Z,#1639,COPY_2 Jump with ENTER.
1631 CP ":"
1633 JR Z,#1639,COPY_2 Also jump with ':'.
1635 LD (#1E00),A Otherwise store character.
1638 RST #28,NEXT_C_RAM Update CH_ADD again.
1639 COPY_2 CALL #0409,ST_END_RAM Confirm end of statement and exit
during syntax checking.
163C LD A,(#1E00)
163F CP "1" Normal screendump if '1' followed the
1641 CALL Z,#164C,COPS 'SCREEN$'.
1644 CP "2" Grey scale in case of a '2'.
1646 CALL Z,#16B2,COPS2 Ignore other values.
1649 JP #0419,END Finished.
THE 'NORMAL SCREENDUMP' SUBROUTINE
This routine dumps a normal screendump to the printer. It can be called also by using
command code 58 (#3A).
164C COPS LD HL,16384 Start of screen.
164F LD DE,#02BA Print the escape sequence for n/72 inch
1652 CALL #1779,PO_ESC_SEQ line feeds.
1655 LD A,8 Make it 8/72.
1657 CALL #1944,PNTP
165A C1_LINE LD DE,#02C2 Print the escape sequence for a normal
165D CALL #1779,PO_ESC_SEQ screendump. (60 dpi)
1660 LD A,0 Signal '256 dot columns will follow' to
1662 CALL #1944,PNTP the printer.
1665 LD A,1
1667 CALL #1944,PNTP
166A PUSH HL
166B C1_CHAR LD B,8 Eight pixels in each byte.
166D C1_PIXEL PUSH HL
166E C1_PIXROW CALL #1751,PIXEL_COL Get pixel colour.
1671 AND #04
1673 JR NZ,#1676,C1_ADD_DOT Jump with colour codes 4-7 (no dot).
1675 SCF Set a dot for colour codes 0-3.
1676 C1_ADD_DOT LD A,(#1978) Incorporate one dot in dot column.
167A LD (#1978),A
167D INC H Next pixel row.
167E LD A,H
167F AND #07
1681 JR NZ,#166E,C1_PIXROW Repeat until all eight pixelrows have
1683 LD A,(#1978)
1686 CALL #1944,PNTP Print the dot column.
1689 POP HL Repeat until all eight pixels in a byte
168A DJNZ #166D,C1_PIXEL have been printed. One character cell (64
pixels) has been printed now.
168C INC L Next character position.
168D LD A,L
168E AND #1F
1690 JR NZ,#166B,C1_CHAR Loop for all 32 character columns.
1692 CALL #16A2,ADV_PAPER Advance printer paper one line.
1695 POP HL
1696 LD A,H
1697 ADD A,8 Make HL point to the next screen third.
1699 LD H,A 'N_CHARROW' will adjust HL if necessary.
169A CALL #176C,N_CHARROW Calculate the address of the next
169D JR NZ,#165A,C1_LINE characterrow and loop until end of
pixel area reached.
169F JP #1745,DUMP_EXIT Exit via 'DUMP_EXIT' to reset printer.
THE 'ADVANCE PRINTER PAPER' SUBROUTINE
This subroutine advances the paper by sending a CR (carriage return) and (when needed)
a LF (line feed) to the printer.
16A2 ADV_PAPER LD A,13 Send a CR to the printer.
16A4 CALL #1944,PNTP
16A7 LD A,(#02A0) This is 'LFEED'.
16AA AND A
16AB RET Z Return if no LF has to be printed.
16AC LD A,10 Otherwise send a LF.
16AE CALL #1944,PNTP
16B1 RET Finished.
THE 'GREYSCALE SCREENDUMP' SUBROUTINE
This routine prints a large screendump. It can also be called by using
command code 66 (#42).
NOTE: With System 3b this routine printed a greyscale dump but with the System 3c
'improvement' of the 'PIXEL_CLR' subroutine the greyscales have been limited to black
and white only. The routine now just produces a larger screendump (3*3 dots for each
16B2 COPS2 LD HL,#57E0 Address of the lowest pixelrow of the
charactersquare in the bottom left corner.
16B5 LD DE,#02BA Print the escape sequence for n/72 inch
16B8 CALL #1779,PO_ESC_SEQ line feeds.
16BB LD A,6 Make it 6/72.
16BD CALL #1944,PNTP
16C0 LD B,128 There are 128 2-pixel columns.
16C2 LD C,8 8 pixels make one byte. Start with
leftmost bit in a byte.
16C4 C2_2PIXCOL PUSH BC
16C5 PUSH HL
16C6 LD DE,#02EA Print the escape sequence for the
16C9 CALL #1779,PO_ESC_SEQ greyscale bitimage mode.
16CC LD B,24 There are 24 characterrows.
16CE C2_SCRROW PUSH BC
16CF PUSH HL
16D0 LD B,8 A character has 8 pixelrows.
16D2 C2_PIXROW PUSH BC
16D3 PUSH HL
16D4 LD DE,#1BD6 Clear the buffer for the 2 pixels.
16D7 LD B,3
16D9 C2_CLRBUF XOR A
16DA LD (DE),A
16DB INC DE
16DC DJNZ #16D9,C2_CLRBUF
16DE LD B,2 The dot columns for 2 pixels are build
up each time.
16E0 C2_2PIX PUSH BC
16E1 PUSH HL
16E2 LD B,C
16E3 CALL #1751,PIXEL_COL Get the colour of the (B-1)th pixel.
16E6 AND #07 Keep only the least significant 3 bits.
16E8 INC A Make the range 1..8.
16E9 LD B,A
16EA LD C,0 Set the bit in the C register which
16EC SCF corresponds to the colour.
16ED C2_MK_MASK RL C
16EF DJNZ #16ED,C2_MK_MASK
16F1 LD DE,#02F2 DE points to the 'GREYSCALE' table.
16F4 LD HL,#1BD6 HL points to the 2-pixel buffer.
16F7 LD B,3 Each pixel is printed as 3*3 dots.
16F9 C2_DOTCOL PUSH BC
16FA LD B,3
16FC C2_DOTROW LD A,(DE) Get colour pattern.
16FD AND C Only keep the bit with the right colour.
16FE LD A,(HL)
16FF JR Z,#1702,C2_ADD_DOT Jump if bit isn't set.
1701 SCF Otherwise set this dot.
1702 C2_ADD_DOT RL A Incorporate this dot.
1704 LD (HL),A
1705 INC DE Next entry in 'GREYSCALE' table.
1706 DJNZ #16FC,C2_DOTROW Repeat for 3 dotrows.
1708 INC HL
1709 POP BC
170A DJNZ #16F9,C2_DOTCOL Repeat for 3 dotcolumns.
170C POP HL
170D POP BC
170E DEC C Next pixel.
170F DJNZ #16E0,C2_2PIX Two pixels are handled at a time.
1711 LD B,3 Three dotcolumns are to be printed.
1713 LD HL,#1BD6
1716 C2_PRT3X3 LD A,(HL) Print each dotcolumn in turn.
1717 CALL #1944,PNTP
171A INC HL
171B DJNZ #1716,C2_PRT3X3 Repeat for all three.
171D POP HL
171E DEC H Next pixelrow.
171F POP BC Repeat for the eight pixelrows in a
1720 DJNZ #16D2,C2_PIXROW character square.
1722 POP HL
1723 LD A,L One character row up.
1724 SUB 32
1726 LD L,A
1727 JR NC,#172D,C2_CHRROW Jump if still within the same third.
1729 LD A,H Otherwise update MSB of address.
172A SUB 8
172C LD H,A
172D C2_CHRROW POP BC
172E DJNZ #16CE,C2_SCRROW Repeat for the 24 rows on the screen.
1730 CALL #16A2,ADV_PAPER Advance the paper.
1733 POP HL
1734 POP BC
1735 DEC C Skip the two pixels which have already
1736 DEC C been printed.
1737 JR NZ,#173C,C2_BYTE Jump if not all pixels within this byte
have been printed.
1739 LD C,8 Otherwise reset 'pixels in a byte' counter
173B INC HL and point to the next character position
to the right.
173C C2_BYTE DJNZ #16C4,C2_2PIXCOL Repeat for the 128 2-pixelcolumns.
173E LD B,4 Advance the paper for four lines.
1740 C2_ADVPAP CALL #16A2,ADV_PAPER
1743 DJNZ #1740,C2_ADVPAP
1745 DUMP_EXIT LD DE,#02BA Print the escape sequence for n/72 inch
1748 CALL #1779,PO_ESC_SEQ line feeds.
174B LD A,(#029F) Make it (LSPCE)/72.
174E JP #1944,PNTP Exit via 'PNTP'.
THE 'PIXEL COLOUR' SUBROUTINE
In System 3b this routine returned with the low 3 bits of the A register holding the
colour of the Bth pixel from address HL (i.e. the paper colour for an 'off' pixel and
the ink colour for an 'on' pixel). Because some normal screen dumps came out as a solid
black mess the routine was somewhat changed in System 3c (from #1762-#1764). The
routine now returns with %111 for an on pixel and with %000 for an off pixel. However
now the greyscale dump is reduced to a 'no more greyscales' large screendump.
1751 PIXEL_COL PUSH HL Save address of current 8-pixels.
1752 PUSH BC Save pixel number (range 1..8).
1753 XOR A
1755 PIXEL_COL1 RLA Now set (B-1)th bit of A (range 0..7).
1756 DJNZ #1755,PIXEL_COL1
1758 AND (HL) Zero flag now reflects state of pixel
(i.e. set means pixel set).
1759 PUSH AF These seven instructions don't serve
175A LD A,H any purpose anymore. They were used in
175B RRCA Sys 3b to calculate the attribute
175C RRCA address.
175E AND #03
1760 OR #58
1762 POP AF Restore flags.
1763 LD A,#38 PAPER 7, INK 0.
1765 POP BC
1766 POP HL
1767 RET NZ Return with %000 if pixel was set.
1768 RRCA Otherwise move bit3-5 to bit0-2.
176B RET Return with %111.
THE 'NEXT CHAR. ROW ADDRESS' SUBROUTINE
This subroutine calculates the address of the next characterrow, if the end of the
pixel area is reached a return with Zero set will be made.
176C N_CHARROW LD A,L Update low address byte to next character
176D ADD A,32 The carry will be reset within display
176F LD L,A thirds.
1770 CCF Invert carry.
1771 SBC A,A A holds #FF within same third, 0 else.
1772 AND #F8 A will hold #F8 (i.e. -8) within a
1774 ADD A,H third, but 0 when a new third is
1775 LD H,A reached. Update high byte (which was
already incremented by 8).
1776 CP #58 Return with the Zero flag set if
1778 RET attributes reached.
THE 'PRINT ESCAPE SEQUENCE' SUBROUTINE
This subroutine is used to send escape sequences to the printer. The start of the
sequence is held in the DE register, a sequence ends with a CHR$ 128.
1779 PO_ESC_SEQ LD A,(DE) Fetch a code.
177A CP 128
177C RET Z Exit if it's 128.
177D CALL #1944,PNTP Otherwise send it to the printer.
1780 INC DE
1781 JR #1779,PO_ESC_SEQ Continue until the sequence is finished.
THE '"P" CHANNEL OUTPUT' ROUTINE
This routine handles the DISCiPLE's "P" channel, the @6 system variable (PCODE) signals
if it's to be handled as a "t" or a "b" channel. (As with the Opus Discovery and the
ZX Interface 1.) This routine handles also the sending of the CATalogue over the network
whenever a pupil gives the 'CAT' command.
1783 PCHAN_OUT LD (#1978),A
1786 CALL #09FB,TEST_SERV
1789 JR Z,#1796,PCHAN_OUT1 Jump if not serving the network.
178B PUSH IX When serving the network the byte to be
178D LD A,(#1978) printed is send over the network.
1790 CALL #2966,JN_OUTPUT
1793 POP IX
1796 PCHAN_OUT1 LD A,(#029E) This is PCODE.
1799 AND A
179A LD A,(#1978) Fetch the code to be send to the
179D JP NZ,#1944,PNTP printer, send it right away if
(PCODE)=1, i.e. when the DISCiPLE
17A0 LD HL,(#1974) Jump to the appropriate 'output'
17A3 JP (HL) routine.
This is the normal 'output' routine, but a few (control) characters are followed by
one or two operands, these have to be handled different. This is done by altering the
'output' routine address.
17A4 P_ALL LD HL,#029D This is 'WIDTH'.
17A7 CP 32
17A9 JP NC,#1892,P_NOCTRL Jump if not a control code (>=32).
17AC CP 6 This is the "PRINT comma" code.
17AE JP C,#184D,P_ESCAPE Jump with codes < 6.
17B1 JR NZ,#17C1,P_NOCOMMA Jump with codes > 6.
17B3 LD A,(HL) Fetch the number of characters per
17B4 SRL A line, divide it by two.
17B6 LD B,A
17B7 LD HL,#1976 #1976 holds the position on the current
line (i.e. the number of characters
already printed on this line).
17BA SUB (HL)
17BB JR C,#17E2,P_NEWLINE Jump if already on 2nd half of line.
17BD LD H,B Otherwise jump with H holding the
17BE JP #1864,P_TAB center position of the line.
17C1 P_NOCOMMA CP 8 This is "cursor left" or "backspace".
17C3 JP C,#184D,P_ESCAPE Jump with codes < 8.
17C6 JR NZ,#17D4,P_NOBACK Jump with codes > 8 (examine further).
17C8 LD HL,#1976 Get current position.
17CB LD A,(HL)
17CC AND A
17CD RET Z Return if already on leftmost position.
17CE DEC (HL) Otherwise decrement current position.
17CF LD A,127 This isn't "BACKSPACE", this is
17D1 JP #1944,PNTP Print a "DELETE".
17D4 P_NOBACK CP 13 This is "ENTER" or "CARRIAGE RETURN".
17D6 JR C,#184D,P_ESCAPE Jump with codes < 13.
17D8 JR NZ,#180E,P_NOENTER Jump with codes > 13.
17DA LD HL,#1977 This flag, when set, indicates that a
17DD BIT 0,(HL) newline has already been send to the
printer. I.e. the previous line was full
17DF RES 0,(HL) Reset the flag.
17E1 RET NZ Return if this newline has been send
17E2 P_NEWLINE LD HL,#1977 Signal 'newline has been send'.
17E5 RES 0,(HL)
17E7 LD HL,#1976
17EA LD (HL),0 Set current position to 0.
17EC LD A,(#02A0) Fetch (LFEED), the number of line feeds
17EF AND A needed after a carriage return.
17F0 JR Z,#17FA,P_CARRET Jump if it is 0.
17F2 LD B,A Otherwise send the line feeds.
17F3 P_LFEED LD A,10 CHR$ 10 is line feed.
17F5 CALL #1944,PNTP
17F8 DJNZ #17F3,P_LFEED Loop until (LFEED) line feeds send.
17FA P_CARRET LD A,13 Now send the carriage return.
17FC CALL #1944,PNTP
17FF LD A,(#02A1) Fetch (LMARG), that is the left margin.
1802 AND A
1803 RET Z Return if it is 0.
1804 LD B,A Otherwise send (LMARG) spaces.
1805 LD (HL),A Adjust current print position.
1806 P_LMARG LD A,32
1808 CALL #1944,PNTP
180B DJNZ #1806,P_LMARG Loop until (LMARG) spaces send.
180D RET Finished.
Now the control codes with operands are handled. The control codes from INK to OVER
(16..21) and ESC (27) require a single operand, whereas the control characters AT & TAB
are required to be followed by two operands. The following routines leads to the control
character code being stored in TVDATA-lo, the first operand in TVDATA-hi or the A
register if there is only a single operand required, and the second operand in the
A register. The ESC control code is handled separately, the single operand is send
directly to the printer.
180E P_NOENTER CP 16 This is "INK control".
1810 JR C,#184D,P_ESCAPE Jump with codes < 16.
1812 CP 24 This is "TAB control"+1.
1814 JR NC,#184D,P_ESCAPE Jump with codes >= 24.
1816 CP 22 This is "AT control".
1818 JR NC,#1848,P_2_OPER Jump with AT & TAB.
181A LD DE,#1827,P_CONT Otherwise the '"P" channel output'
routine is to be changed to 'P_CONT'.
181D P_TV_1 LD (23566),A Store the control character code in
The current 'output' routine address is changed temporarily.
1820 P_CHANGE LD HL,#1974 HL points to the 'output' routine
1823 LD (HL),E address. Enter the new 'output' routine
1824 INC HL address and thereby force the next
1825 LD (HL),D character to be considered as an
1826 RET operand.
Once the operands have been collected the routine continues.
1827 P_CONT LD DE,#17A4,P_ALL Restore the original address for
182A CALL #1820,P_CHANGE 'P_ALL'.
182D LD HL,(23566) Fetch the control code and the first
operand if there are indeed two
1830 LD D,A The 'last' operand and the control code
1831 LD A,L are moved.
1832 CP 22
1834 JR C,#183A,P_CO_TEMPS Jump if handling INK to OVER.
1836 JR NZ,#1864,P_TAB Jump if handling TAB.
1838 JR #188F,P_AT Jump if handling AT.
The control codes INK to OVER are handled by the 'main' ROM 'CO_TEMP' routine. It is
entered with the control code in the A register and the parameter in the D register.
Note that all changes are to the 'temporary' system variables.
183A P_CO_TEMPS LD HL,#2211,CO_TEMP_5 Return via the calling routine to
183D EX (SP),HL 'CO_TEMP' in the 'main' ROM.
183E PUSH HL
1840 P_TV_2 LD DE,#1827,P_CONT Store the first operand in TVDATA-hi
1843 LD (23567),A and change the address of the 'output'
1846 JR #1820,P_CHANGE routine to 'P_CONT'.
Enter here when handling the control codes AT & TAB.
1848 P_2_OPER LD DE,#1840,P_TV_2 The control code will be stored in
184B JR #181D,P_TV_1 TVDATA-lo and the address of the
'output' routine changed to 'P_TV_2'.
184D P_ESCAPE CP 27
184F JR NZ,#1860,P_QUEST Print a '?' if it isn't ESC.
1851 LD DE,#1857,P_ESC Otherwise change the address of the
1854 JP #1820,P_CHANGE 'output' routine to 'P_ESC'.
Enter here when handling the ESC control code, the character code following the ESC
is send directly to the printer.
1857 P_ESC LD DE,#17A4,P_ALL Restore the original address for
185A CALL #1820,P_CHANGE 'P_ALL'.
185D JP #1944,PNTP Send the code following the ESC to the
A question mark is printed whenever an attempt is made to print an unprintable
1860 P_QUEST LD A,63 The character '?'.
1862 JR #1892,P_NOCTRL Send it to the printer.
Now deal with the TAB control code.
1864 P_TAB LD A,(#029D) Fetch (WIDTH), that is the line length.
1867 LD B,A
1868 LD A,H Fetch the position where to TAB (or AT)
1869 SUB B to.
186A JR C,#1872,P_INRANGE Jump if position is on this line.
186C LD HL,#046C,REPORT_B Otherwise return to 'REPORT_B' in the
186F EX (SP),HL 'main' ROM ('Integer out of range').
1870 PUSH HL
1872 P_INRANGE LD A,(#1976) Fetch current position.
1875 LD B,A
1876 LD A,H
1877 SUB B
1878 PUSH HL Print on a new line if print position
1879 CALL C,#17E2,P_NEWLINE exceeds TAB position.
187C POP HL
187D LD A,(#1976) Fetch the current position again.
1880 SUB H Calculate the number of spaces wanted.
1881 RET Z Return if already there.
1882 CPL The number is negative so make it
1883 INC A positive.
1884 LD B,A Print the needed spaces.
1885 P_SPACE LD A,32
1887 PUSH BC
1888 CALL #17A4,P_ALL
188B POP BC
188C DJNZ #1885,P_SPACE
Enter here when handling AT.
188F P_AT LD H,D Store the second operand and continue
1890 JR #1864,P_TAB in the TAB routine.
The 'not control' characters are divided into four groups: the ordinary characters,
the tokens, the graphics and the user-defined graphics.
1892 P_NOCTRL CP 128 This is the first graphic.
1894 JR C,#18FD,P_ASCII Jump with ASCII characters (< 128).
1896 CP 144 This is the first UDG.
1898 JR NC,#18A3,P_TOK&UDG Jump with UDG's and tokens.
189A LD B,A Construct the graphic in the
189B RST #10,CALBAS calculator's memory area by calling
189C DEFW #0B38,PO_GR_1 'PO_GR_1' in the 'main' ROM.
189E LD HL,23698 HL points to the start of the graphic
form; i.e. MEMBOT.
18A1 JR #18BA,P_GRAPH Jump to print the graphic character.
18A3 P_TOK&UDG SUB 165 This is the RND token.
18A5 JR C,#18AD,P_UDGS Jump with UDG's (< 165).
18A7 LD HL,#0C10,PO_TOKENS The routine indirectly jumps to the
18AA EX (SP),HL 'PO_TOKENS' routine in the 'main' ROM
18AB PUSH HL to expand the token. That routine then
18AC RET calls recursively the 'P_ALL' routine
above for each character of the token.
18AD P_UDGS ADD A,21 Adjust range, UDG's now from 0..20.
18AF LD BC,(23675) BC points to the start of the UDG area
18B3 LD H,0 (UDG).
18B5 LD L,A Pass the code to HL.
18B6 ADD HL,HL Each UDG is made by eight bytes, so
18B7 ADD HL,HL multiply the code by eight.
18B8 ADD HL,HL
18B9 ADD HL,BC
18BA P_GRAPH LD DE,#1964 Move the eight bytes to the DISCiPLEs
18BD LD BC,8 internal printerbuffer.
Now the eight pixelrows are converted to eight dotcolumns.
18C2 PUSH IX
18C4 LD IX,#1973 The last address of the dotcolumns.
18C8 LD B,8 Each graphic has eight pixelrows.
18CA P_GRAPH1 LD HL,#1964 Address of the graphic's pixelrows.
18CD LD C,8 Each pixelrow has eight pixels.
18CF P_GRAPH2 LD D,(HL) Each bit is moved in turn into the E
18D0 RR D register.
18D2 LD (HL),D
18D3 RL E
18D5 INC HL
18D6 DEC C
18D7 JR NZ,#18CF,P_GRAPH2 Repeat for the eight pixels.
18D9 LD (IX+0),E Store the dotcolumn.
18DC DEC IX
18DE DJNZ #18CA,P_GRAPH1 Repeat for the eight rows.
18E0 POP IX
18E2 LD DE,#02C2 Print the escape sequence for 60 dpi.
18E5 CALL #1779,PO_ESC_SEQ
18E8 LD A,8 Signal to the printer 'there follow
18EA CALL #1944,PNTP eight bytes of bitimage data'.
18ED LD A,0
18EF CALL #1944,PNTP
18F2 LD B,8 Send the eight bytes to the printer.
18F4 P_GRAPH3 LD A,(HL)
18F5 CALL #1944,PNTP
18F8 INC HL
18F9 DJNZ #18F4,P_GRAPH3
18FB JR #192F,P_UP_POS Update the current position.
Now deal with the printing of normal ASCII characters.
18FD P_ASCII LD HL,#1977
1900 RES 0,(HL) Reset 'newline already send' flag.
1902 LD (#1978),A
1905 LD A,(#02A2) Fetch (GRAPH), when it's 1 the DISCiPLE
1908 AND A has to generate the graphic
1909 LD A,(#1978) representation of some characters.
190C JR Z,#192C,P_OTHERS Jump if the normal code has to be send.
Because some Spectrum characters aren't supported by all printers the DISCiPLE can
send the graphic representation of those characters instead of the original character
code. The characters supported by System 3d are £, # and ©.
190E CP "£"
1910 JR NZ,#1918,P_NOPOUND Jump if it isn't '£'.
1912 LD HL,#02D2 Point to the bitimage data for £.
1915 JP #18BA,P_GRAPH Handle it as an ordinary graphic.
1918 P_NOPOUND CP "#"
191A JR NZ,#1922,P_NOPOWER Jump if it isn't '#'.
191C LD HL,#02DA Point to the bitimage data for #.
191F JP #18BA,P_GRAPH Handle it as a graphic.
1922 P_NOPOWER CP "©"
1924 JR NZ,#192C,P_OTHERS Jump to handle all non '©' characters.
1926 LD HL,#02E2 Point to the bitimage data for ©.
1929 JP #18BA,P_GRAPH Handle it as a graphic.
Finally the normal characters can be send to the printer.
192C P_OTHERS CALL #1944,PNTP Send the character to the printer.
192F P_UP_POS LD A,(#1976) Update the current position.
1932 INC A
1933 LD (#1976),A
1936 LD HL,#029D HL points to WIDTH.
1939 SUB (HL)
193A RET C Return if the line isn't full yet.
193B CALL #17E2,P_NEWLINE Otherwise someone has forgotten that
193E LD HL,#1977 printer lines aren't endless, so print
1941 SET 0,(HL) a 'NEWLINE' and signal 'ignore next
1943 RET character if it is a CR'.
THE 'SEND A BYTE TO PRINTER' SUBROUTINE
This routine is also called by using command code 57 (#39). It sends the 8 bit code in
the A register to the printer port, after checking if the printer is busy. The BREAK
key is tested.
1944 PNTP LD (#1978),A Store the code temporarily.
1947 PNTP_1 CALL #03FA,TEST_BREAK Exit if the BREAK key is pressed.
194A IN A,(31) Test the BUSY line of the printer.
194C BIT 6,A
194E JR Z,#1947,PNTP_1 Wait until printer isn't BUSY.
1950 LD A,(#1978) Send the code to the printer port.
1953 OUT (251),A
1955 LD A,(#1DDA) Fetch current control port status.
1958 OR #40 Give a STROBE.
195A OUT (31),A
195C AND #BF Reset STROBE.
195E OUT (31),A
1960 LD A,(#1978) Return with the A register holding the
1963 RET outputted byte.
THE 'PRINTER WORKSPACE'
Here follows the workspace used by the printer routines.
1964 DEFS 8
196C DEFS 8
1974 DEFW #17A4 Address of 'output' routine for "P".
1976 DEFB 0 Holds the current print position.
1977 DEFB 0 The 'ENTER' flag.
1978 DEFB 0 Temporary store for byte to be send.