had no
address bus - program and data memory access were
contained in separate units, which reduced the number of pins
and the associated cost. It also featured 64
registers,
eight, which meant external
RAM wasn't always needed for
small applications. In addition, the 2-chip processor didn't
need support chips, unlike others which needed seven or more.
The F8 inspired other similar
CPUs, such as the
Intel8048. The use of the ISAR register allowed a subroutine to
be entered without saving a bunch of registers, speeding
execution - the ISAR would just be changed. Special purpose
registers were stored in the second cell (regs 9-15), and the
first eight registers were accessed directly. The windowing
concept was useful, but only the register pointed to by the
ISAR could be accessed - to access other registers the ISAR
was incremented or decremented through the window.
(1994-11-16)