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Function
Signal
Name
External Clock
EXPCLK
nMEDCHG /
nBROM
Interrupts
nEXTFIQ
EINT[3]
nEINT[1-2]
nPWRFL
BATOK
Power
nEXTPWR
Management
nBATCHG
62
Signal
I/O
Expansion clock rate is the same as the CPU clock for 13 MHz and
18 MHz. It runs at 36.864 MHz for 36,49 and 74 MHz modes; in
13 MHz mode this pin is used as the clock input.
I
Media changed input; active low, deglitched. Used as a general pur-
pose FIQ interrupt during normal operation. It is also used on power
up to configure the processor to either boot from the internal Boot
ROM, or from external memory. When low, the chip will boot from the
internal Boot ROM.
I
External active low fast interrupt request input
I
External active high interrupt request input
I
Two general purpose, active low interrupt inputs
I
Power fail input; active low, deglitched input to force system into the
Standby State
1
I
Main battery OK input; falling edge generates a FIQ, a low level in the
Standby State inhibits system start up; deglitched input
I
External power sense; must be driven low if the system is powered by
an external source
1
I
New battery sense; driven low if battery voltage falls below the "no-
battery" threshold; it is a deglitched input
Table 29. External Signal Functions (cont.)
Description
DS508UM1
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