HARDWARE REFERENCE A
3-4
3.2.3 i960 Jx/Hx CPU Counter/Timers
The i960 Jx and Hx processors are equipped with two on-chip counter/timers. These timers are clocked
at the CPU clock rate which does not correspond exactly with the CPU Module Frequency Switch
settings. Use Table 3-3 to determine the exact CPU clock frequency.
3.2.4 CPU Module V
PP
Switch
The V
PP
Switch (switch position 1 in Table 3-2) enables/disables V
PP
to the boot Flash ROMs located
on the CPU module. It is recommended that this switch remains set to OFF (the default setting from the
factory). When V
PP
is enabled (switch in ON position), the processor may not be able to boot from
ROM if the power sequencing of +5V and +12V is not correct.
3.3 CPU MEMORY MAP
As indicated in Figure 3-2, the memory map is organized to take advantage of the i960 Cx, Hx, and Jx
processors’ bus sizing capabilities. Memories and I/O devices are described in the sections following
the figure.
Table 3-3. i960 Jx/Hx CPU Clock Rates
CPU Frequency
Switch Setting
CPU Clock Frequency
16 MHz 16.11 MHz
20 MHz 20.05 MHz
25 MHz 25.06 MHz
33 MHz 33.41 MHz
40 MHz 40.09 MHz
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