The user can set the bit
PCON.1
to drive this chip entering
POWER-DOWN
mode.
In the
POWER-DOWN
mode, the on-chip oscillator is stopped. The contents of on-chip RAM and
SFRs are maintained.
The power-down mode can be woken-up by either hardware reset or
/INT0, /INT1, /INT2
and
/INT3
external interrupts. When it is woken-up by
RESET
pin, the program will execute from the address
0x0000, and be carefully to keep
RESET
pin active for at least 10ms in order to get a stable clock
while waking up this chip from
POWER-DOWN
mode. If it is woken-up from I/O, the program will
jump to related interrupt service routine. To use I/O wake-up, interrupt-related registers have to be
programmed accurately before power-down is entered.
Pay attention to add at least one “NOP”
instruction subsequent to the power-down instruction if I/O waken-up is used.
Mode
Idle
Idle
Power-Down
Power-Down
Program Memory
Internal
External
Internal
External
ALE
1
1
0
0
PSEN
1
1
0
0
Port0
Data
Float
Data
Float
Port1
Data
Data
Data
Data
Port2
Data
Address
Data
Data
Port3
Data
Data
Data
Data
Pin Status in IDLE Mode and POWER-DOWN Mode
3. POWER-ON FLAG (POF)
The register bit in PCON.4 is set only by power-on action. System RESET from
watch-dog-timer, software RESET and RESET pin can not set this bit. It can be cleared by
firmware.
In System Programming (ISP)
To develop a good program for ISP function, the user has to understand the architecture of
the embedded flash.
The embedded flash consists of 30 pages. Each page contains 512 bytes.
Dealing with flash, the user must erase it in page unit before writing (programming) data
into it.
Erasing flash means setting the content of that flash as
FFh.
Two erase modes are available in this
chip. One is
mass mode
and the other is
page mode.
The
mass mode
gets more performance, but
it erases the entire flash. The page mode is something performance less, but it is flexible since it
erases flash in page unit.
Unlike RAM’s real-time operation, to erase flash or to write (program) flash often takes longer time
to finish.
MEGAWIN
MPC89x515A Data Sheet
27