NVM register: OR1 (Option Register 1):
Bits-7
Bits-6
Bits-5
Bits-4
Bits-3
Bits-2
Bits-1
Bits-0
FZWDTCR
OSCDN
HWBS
EN6T
FZWDTCR: Used to freeze the WDT-controlling register.
0:= Configure the SFR WDTCR to be reset only via power-up action; not by software
reset nor reset from the Watch Dog Timer.
1:= (default) Permit all the reset events from power-up, software and the Watch Dog Timer
could reset the SFR WDTCR.
OSCDN: Used to adjust the behavior of crystal oscillator.
0:= The DC gained of crystal oscillator amplifier is doubled but bandwidth is reduced. It will bring
help to EMI reducing and improve the power consumption. Dealing with application, it does
not need high frequency clock (under 20MHz). It is recommended to do so.
1:= The gained of crystal oscillator is enough for oscillator to start oscillating up to 48 MHz.
HWBS: Used to configure the MPC89x51A boot from ISP program or normal application program after the
power-on sequence.
0:= The MPC89x51A will boot from ISP start address after power-on.
1:= No operation. The MPC89x51A will boot from normal application program.
EN6T: Used to configure the MPC89x51A run in 6T 12T mode or 6T mode.
0:= The MPC89x51A will run in 6T mode
1:= The MPC89x51A will run in 12T mode
The default value of the OR1 is FFh.
RAM
There are 512 bytes RAM built in MPC89x51A.
The user can visit the leading 128-bytes RAM via direct addressing instructions, we have named
those RAM as direct RAM that occupies address space 00h to 7Fh.
Followed 128-bytes RAM can be visited via indirect addressing instructions, we have named
those RAM as indirect RAM that occupied address space 80h to FFh.
The other 256-bytes RAM is named expanded RAM that still occupied address space 00h to FFh.
An user can access it via general register Ri, or via data pointers DPTR associated with MOVX
instructions, say MOVX A, @R1 or MOVX A, @DPTR. To reserve the natural characteristic of
instruction MOVX which is designed to access external memory, the user can set the bits ERAM
in SFR AUXR as 1, and by doing so is to hide the expanded RAM and to visit the external
memory.
MEGAWIN
MPC89x51A Data Sheet
11
MEGAWIN [ MEGAWIN TECHNOLOGY CO., LTD ]
