121

..

is a printer, each data line corresponds to one pin on the print head. Thus each byte sent will fire up to eight pins.

But the printer has 9 pins available. So how do you fire the ninth pin with only 8 data lines? In fact, do you really want to bother with just one extra pin? For this purpose, your printer has a special 9-pin graphics mode (it won’t, however, work with 7-bit interface systems). In this mode the printer takes 2 bytes to fire all 9 pins as shown in Figure 7-8. For such

graphics-intensive applications as screen dumps, printing 9 pins at a time can speed up the process considerably.

0

128

 

L

 

64

 

:

32

 

E

16

) First byte

0

8

 

 

4

 

 

2

 

:

I

!

0

128

Second byte

 

(only the top bit is used)

Figure 7-8.The printer needs 2 bytes to tire all 9 pins in the 9-pin

graphics mode.

In addition, you can select the print density by the value qf n0. When nO is 0 the normal density is selected, and when nO is 1 the double density is selected.

Since computers are faster than printers, there is no signif- icant time loss in printing a single line of graphics with 9 pins. You get 9 dots per line in about the same time as you get 8 dots in the other graphics modes.

Page 127
Image 127
Star Micronics ND-10/15 user manual Printer needs 2 bytes to tire all 9 pins in the 9-pin