Mnemonic
Type Name and Function
Address Latch Enable: Output pulse for latching the low byte of the
address during an access to external memory. In normal operation, ALE
O (I) is emitted at a constant rate of 1/6 the oscillator frequency, and can be
used for external timing or clocking. Note that one ALE pulse is skipped
during each access to external data memory.
ALE
Program Store ENable: The read strobe to external program memory.
When executing code from the external program memory, PSEN is
PSEN
EA
O
I
activated twice each machine cycle, except that two PSEN activations
are skipped during each access to external data memory. PSEN is not
activated during fetches from internal program memory.
External Access Enable: EA must be externally held low to enable the
device to fetch code from external program memory locations.
Crystal 1: Input to the inverting oscillator amplifier and input to the
internal clock generator circuits.
XTAL1
XTAL2
I
O
Crystal 2: Output from the inverting oscillator amplifier
4
80C32E
4149M–AERO–06/03
AIMTEC [ AIMTEC ]
