RAM
There are 256 bytes RAM built in MPC82x52A.
The user can visit the leading 128-byte RAM via direct addressing instructions, and we name
those RAM as direct RAM that occupies address space 00h to 7Fh.
Followed 128-byte RAM can be visited via indirect addressing instructions, and we name
those RAM as indirect RAM that occupied address space 80h to FFh.
Since the MPC82x52A has 256 bytes RAM only, any instruction to access RAM addressing
over FFH is inhibited. Furthermore, since the MPC82x52A is lack of PORT0 and PORT2 to
address chip-external memory, all MOVX instructions are inhibited.
Nonvolatile Registers:
There are four Nonvolatile Registers named OR0, OR1, OR2, and OR3 individually. They are
designed to configure the MPC82x52A, i.e., to decide to use internal RC oscillator or use
crystal oscillator as oscillating source, or to allocate the built-in flash for application program,
application data and In-System-Program code.
Generally, the only way to program those four nonvolatile registers is making use of a popular
NVM writer, such as: Hi-Lo System All-11, Leaper-48 and Megawin-Provided MCU writer. The
user’s program and the ISP program never can change those option registers.
NVM register: OR0 (Option Register 0):
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
LVFWP
ENLVR
ISPAS1
ISPAS0
HWBS
reserved1
SB
LOCK
LVFWP: = Low-Voltage-Flag-Write-Protecting bit.
0: =
inhibit the flash read/write action via ISP/IAP mechanism while the power supply drops
under a specific voltage level. Typically, the Low-Voltage is identified to 3.7V/2.3V
(Operate in the 5V / 3V) associated with 12 MHz oscillator.
1: = (default)
No inhibition on the flash-writing action.
ENLVR: = Enable-Low-Voltage-Reset
0: =
Clearing the bit will reset the device while the power supply drops under a specific voltage
level. Typically, the Low-Voltage is identified to 3.7V/2.3V (Operate in the 5V / 3V)
associated with 12 MHz oscillator.
1: = (default)
Setting the bit implies never reset the device in spite of voltage dropping.
16
MPC82x52A Data Sheet
MEGAWIN
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