Commodore CBM - 6 System Information; Organization of the PET System

CHAPTER 6
System Information
ORGANIZATION Of THE PET SYSTEM
The organization of the PET system is shown in Figure 6-1. The PET is
built around the 6502 microprocessor. The display seree n, cassette tape
unit, and keyboard are physical devices
that have been described in Chapter
2. The three external
1/0 ports are interfaced through the 2K block of
memory-mapped
1/0. On 4K/8K PETs, the cassette tape unit connects directly to
the 1/0 block, and the Cassette Tape Interface
is available for connecting a second
cassette unit.
On 16K/32K PETs the cassette tape unit is connected through the
Cassette Tape Interface; additional tape units,
if any are desired, must be inter-
faced through the IEEE 488 port. The six ROM, RAM, and lia blocks are allocated
from the total 65K memory space available on the
PET.
The memory allocation by 4K blocks is shown in Table 6-1. Each portion of
the memory is described in more detail in the following text.
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