
W78E58
- 4 -
Flash
No function in this mode.
EA/V
PP
MODE
DESCRIPTION
Normal
EA
,
External Access, Input, active low.
This pin forces the processor to execute a program from the external ROM. When the
internal flash EEPROM is accessed as in the W78C58, this pin should be kept high.
Flash
V
PP
, Program Power supply pin, Input.
This pin accepts the high voltage (12V) needed for programming the flash EEPROM.
RST
MODE
Normal
DESCRIPTION
RST, Reset, Input, active high.
This pin resets the processor. It must be kept high for at least two machine cycles in
order to be recognized by the processor.
Flash mode configuration pin, Input, active high.
RST is used to configure the flash operations. For details, see
Flash Operations
.
Flash
ALE
MODE
Normal
DESCRIPTION
ALE, Address Latch Enable, Output, active high.
ALE is used to enable the address latch that separates the address from the data on
Port 0. ALE runs at 1/6th of the oscillator frequency. A single ALE pulse is skipped
during external data memory accesses. ALE goes to a high impedance state with a
weak pull-up during reset state.
Flash mode configuration pin, Input, active low.
ALE is used to configure the flash operations. For details, see
Flash Operations
.
Flash
PSEN
MODE
Normal
DESCRIPTION
PSEN,
Program Store Enable, Output, active low.
This pin enables the external ROM onto the Port 0 address/data bus during fetch and
MOVC operations. PSEN goes to a high impedance state with a weak pull-up during
reset state
Flash mode configuration pin, Input, active high.
Flash
PSEN is used to configure the flash operations. For details, see
Flash Operations.
XTAL1
MODE
DESCRIPTION