a E i - Commodore Is Awesome

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stored in the next free location in the
output buffer. If the program is
dealing with a reversed character then
it will store #592 in the next free
location (R VS OFF) and again increment
$4B by #S0 I
When each character has been
fully processed and stored in the output
buffer (including RVS ON and
RVS OFF codes) the Y-register is incremented
by #501. When the Yregister
reaches # $28 one row of text
has been processed and is stored in the
output buffer. The routine at $40AF
then sends the processed data to the
printer, followed by a carriage return.
The X-register is incremented by#S0 I
and compared with #$19. If it is less
than tt $19 then the text screen row
location (stored in #$22 #523) is
incremented by #528 and the whole
process repeated for the next row.
When all rows have been printed
the printer is set to the default font and
the channel to the printer is closed.
Page zero is restored by the routine at
$4291 and the program returns to Basic
as if nothing had happened.
The program works because each
high resolution image on the screen is
actually made up of 64,000 dots (each
individually selectable) arranged in a
definite (though rather complex)
pattern. In much the same way the
printer produces its images using a
pattern of dots, although the way the
dots are organised is very different.
In essence then, this program must
translate the pattern of dots on the
screen, to a pattern recognisable by the
printer, while preserving the image to
be printed.
Because there are 64,000 dots some
or all of which have to be translated
and sent to the printer, it can be seen
that a great deal of processing has to be
done. The programmer/user will want
their printout as quickly as possible (in
business this would be essential - time
is money), so the whole routine has
been written in machine code. This
gives a considerable time saving over
MONITOR: FUNKEY 1
PC SP AC •IP. YP SP
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>055F 0 9 0 6 OA 0 9 0 7 0 6 0 4 [3 5 R AM P.P.1
>0567 5 1 5 9 5 1 3 1 3 6 3 3 3 8 1 4 ..ve i3 1 , kE* 1
>056F OD 4 4 4 C 4 F 4 1 4 4 2 2 4 4 ,
>0577 vikcooac 4 9 5 2 4 5 4 3 5 4 4 F 5 2 5 9 le Nd ftECNN
>057F ET 5 3 5 9 5 3 1 1 3 6 3 6 3 4 ,
F
>05A7
R W 335 VOn M7 5.:3
4 3 4 E 4 3 4 C 5 2 -0
>058F OD 1 4 4 5 3 4 1 5 6 4 5 2 2 5 2 :Pit g l;1 5 Mit4
)0597 5
1M0044N
5 4 € 0 1 ) 4 e 4 5 4 C 5 0 OD I n i.m .n o g
>053F 0 0 e l) 4.10 Oo 0 0 FF FF FF Aw im m kkk
PLUS/4 AND MPS 801 ill
the equivalent Basic program which
took 25 minutes to produce a single
high-res screen dump. In machine code
this process is reduced to three
minutes. This is still fairly slow -but is
the maximum speed obtainable using
the MPS-801 printer. The reason for
this is the size of the printers input
buffer - 90 bytes. A single row of the
high-res screen uses 320 bytes. In order
for the printer to produce a single row
of the high-res screen its buffer must be
filled and emptied four times. This
I MONITOR: GRATEX
PC SR AC XR YR SP
; FFFF 00 FF FF FF F8
• 4000 20 84 42 JSR 14284
• 4003 AD 13 FF LDR $FF13
• 4006 09 D1 C M P 4$131
• 4008 DO OS E N E $403F
• 400A AO 08 L D Y *$08
. 400C 4C 11 40 JMP $4011
• 400F AO 07 L D Y 4107
• 4011 R2 04 L D X 1404
•
•
•
•
•
•
•
•
•
•
.
4068
406E
4070
4071
4073
4074
4076
4078
40711
407E
4080
4C 98 40 RIP 14098
69 20 A D C 4$20
38 S E C
E9 40 S E C 4$40
18 C L C
10 08 E F L t407E
69 40 A D C 1440
99 30 44 STR $443D1Y
4C 92 40 JMP 1.4098
69 40 A D C 4140
28 S E C
• 4012 R9 04 L D A 4004 • 4081 E9 60 S E C 4$60
• 4015 20 BA FF JSR $FFER • 4083 18 C L C
• 4018 A9 00 L D A 4$00 • 4084 10 08 E E L t4OSE
• 401A 20 BD FF JSR $FFED • 4086 69 80 A D C 4$80
• 401D 20 CO FF JSR $FFC0 • 4088 99 3D 44 SIR $443D,Y
. -4020 A2 04 L D X 4404 . 4088 40 98 40 JMP $4098
• 4022 20 C9 FF JSR $FFC9 • 408E 69 60 A D C 4$60
• 4025 RA 00 L D R 4$00 • 4090 38 S E C
• 4027 85 22 S I R 1.22 • 4091 E9 80 S E C 4$80
• 4029 A9 OC L D A 4$0C . 4093 18 C L C
• 402E 85 23 S T P $23 • 4094 10 05 E F L 1.4098
• 40211 A2 00 L D X 4100 • 4096 69 CO A D C 4$C0
• 402F AO 00 L D Y 4$00 • 4098 99 3D 44 SIR $443D.Y
• 4031 98 T Y R . 409E 68 P L R
• 4022 85 48 S I R $48 • 409C R8 T A Y
• 4034 38 S E C • 40913 08 I N Y
• 4035 81 22 L D A ($22),Y • 409E E6 4B I N C $48
• 4037 85 SE S I R $5E • 40A0 AS SD L D A ISD
. 4029 29 7F A N D 4$7F • 40R2 29 80 A N D WO
• 4038 09 22 CMP 4$22 • 40R4 FO 03 B E Q $40A9
• 403D DO 07 B N E $4046 • 40R6 20 F4 40 JSR $40F4
• 403F 18 C L C • 40A9 CO 28 C P Y 4$28
• 4040 A5 5E L D A 15E . 40A2 DO 87 E N E 1.4034
4042 69 05 A D C 4$05 • 40A0 AO 00 L D Y 4100
• 4044 85 SE S I R t5E . 40AF 29 311 44 LDR 1443D.Y
. 4046 RS 5E L D A $5E • 4082 20 D2 FF JSR $FFD2
• 4048 85 5D S I R $511 • 4085 C8 T H Y
• 404A 38 S E C • 40E6 04 48 C P Y 148
. 404P 98 T Y A • 4088 DO ES E N E 1.40AF
• 4040 48 P H A • 40ER R9 OD L D R 4$011
• 404D AS 48 L D A $48 • 40E0 20 D2 FF JSR $FFD2
• 404F R8 T R Y • 408F E8 I N X
• 4050 AS SE L D A $5E • 4000 E0 19 C P X 4$19
• 4052 29 80 A N D 4180 • 4002 DO OE E N E $40112
• 4054 FO 09 H Q 1.405P • 4004 A9 91 L D A 4$91
• 4056 20 E2 40 JSR 140E2 • 4006 20 112 FF JSP tFFD2
• 4059 AS SE L D A 1.5E • 4009 R9 04 L D A 4$04
• 405E 29 7F A N D 417F • 40CE 20 C3 FF JSR $FFC3
. 405D 85 SE S I R $5E • 400E 20 91 42 JSR 14291
• 405F AS SE L D A t5E • 40131 60 R T S
• 4061 E9 20 S E C 4$20 • 4002 18 C L C
• 4063 18 C L C • 4003 A5 22 L D A 1.22
4064 10 08 E F L $405E • 40115 28 A D C #4
. 4066 69 60 A D C 41.60 • 40117 85 22 7 S T A $22
• 4068 99 3P 44 STA $4431),Y • 40119 AS 23
28
L D A $23
Y O U R COMMODOREjanuary1987
105
involves reading 90 bytes of translated
data from the computer - telling the
computer not to send any more data -
printing the 90 bytes now in the input
buffer - request the next 90 bytes and
so on. In other words the printer head
must make four passes for each row of
high
- Budding electronic enthusiasts
res may fi nd a way to make the input
sbuffer c larger and so reduce the printing
rtime, e the rest of us will have to wait two
eminutes. n
.
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