MS51
Dec. 17, 2019
Page
34
of 316
Rev 1.01
M
S51
SE
RIES
TE
CHNICA
L REF
ERE
N
CE MA
NU
A
L
ANL BODCON0,#data
;4 clock cycles
In the first example, the writing to the protected bits is done before the 3-clock-cycle window closes. In
example 2, however, the writing to BODCON0 does not complete during the window opening, there
will be no change of the value of BODCON0. In example 3, the WDCON is successful written but the
BODCON0 write is out of the 3-clock-cycle window. Therefore, the BODCON0 value will not change
either. In Example 4, the second write 55H to TA completes after 3 clock cycles of the first write TA of
AAH, and thus the timed access window is not opened at all, and the write to the protected byte
affects nothing.
SFR Memory Map
6.1.6.3
Addr
0/8
1/9
2/A
3/B
4/C
5/D
6/E
7/F
0
F8
SCON_1
PDTEN
PDTCNT
PMEN
PMD
PORDIS
-
EIP1
EIPH1
1
0
F0
B
CAPCON3
CAPCON4
SPCR
SPCR2
SPSR
SPDR
-
AINDIDS
EIPH
1
0
E8
ADCCON0
PICON
PINEN
PIPEN
PIF
C2L
C2H
EIP
-
1
-
0
E0
ACC
ADCCON1
ADCCON2
ADCDLY
C0L
C0H
C1L
C1H
1
-
-
0
D8
PWMCON0
PWMPL
PWM0L
PWM1L
PWM2L
PWM3L
PIOCON0
PWMCON1
1
0
D0
PSW
PWMPH
PWM0H
PWM1H
PWM2H
PWM3H
PNP
FBD
1
0
C8
T2CON
T2MOD
RCMP2L
RCMP2H
TL2
PWM4L
TH2
PWM5L
ADCMPL
ADCMPH
1
-
-
0
C0
I2CON
I2ADDR
ADCRL
ADCRH
T3CON
PWM4H
RL3
PWM5H
RH3
PIOCON1
TA
1
-
-
0
B8
IP
SADEN
SADEN_1
SADDR_1
I2DAT
I2STAT
I2CLK
I2TOC
1
0
B0
P3
P0M1
P0S
P0M2
P0SR
P1M1
P1S
P1M2
P1SR
P2S
-
IPH
PWMINTC
1
0
A8
IE
SADDR
WDCON
BODCON1
P3M1
P3S
P3M2
P3SR
IAPFD
IAPCN
1
0
A0
P2
-
AUXR1
BODCON0
IAPTRG
IAPUEN
IAPAL
IAPAH
1
0
98
SCON
SBUF
SBUF_1
EIE
EIE1
-
-
CHPCON
1
0
90
P1
SFRS
CAPCON0
CAPCON1
CAPCON2
CKDIV
CKSWT
CKEN
1
0
88
TCON
TMOD
TL0
TL1
TH0
TH1
CKCON
WKCON
1
0
80
P0
SP
DPL
DPH
RCTRIM0
RCTRIM1
RWK
PCON
1
Note
: Unoccupied addresses in the SFR space
marked in “-“ are reserved for future use. Accessing
these areas will have an indeterminate effect and should be avoided.
Table 6.1-1 Special Function Register Memory Map