Commodore PET User Manual page 153

Physieal Deviee Number
The physical device number is a predefined number that refers ta a particu-
lar peripheral unit capable of input and/or output with the PET. The device num-
ber must be within the range 0 ta 255. although currently only numbers 0 ta 30
will assign a device. Deviee numbers are listed in Table 4-1.
Table 4-1. Physieal Deviee Numbers
Deviee Number Deviee
0 Keyboard
1 (default) #1 - Console tape cassette unit
2 #2 - Second tape cassette unit
3 Video display screen
4 through 30 IEEE port devices
31 through 255 Currently unassignable
Seeondary Address Code
The secondary address code specifies the type of operation ta be performed
on the selected device. The meanings of the codes for a particular device are pre-
determined. For the PET tape cassettes. the secondary address code is used by
the PET software primarily ta read or write tape headers. For IEEE 488-interfaced
devices. the secondary address code is passed on directly ta the device. allowing
the program ta select a variety of operational modes. Secondary address codes'
are not used for keyboard input or output ta the display screen. Secondary ad-
dress codes for PET devices are listed in Table 4-2. For IEEE devices. refer ta the
device manual for secondary address codes recognized by the device.
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