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MS51
Dec. 17, 2019
Page
197
of 316
Rev 1.01
M
S51
SE
RIES
TE
CHNICA
L REF
ERE
N
CE MA
NU
A
L
7
6
5
4
3
2
1
0
PnM2.7
PnM2.6
PnM2.5
PnM2.4
PnM2.3
PnM2.2
PnM2.1
PnM2.0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Bit
Name
Description
7:0
PnMn[7:0]
Port 0 mode select
Input Type Select
6.4.2.3
Each I/O pin can be configured individually as TTL input or Schmitt triggered input. Note that all of PxS
registers are accessible by switching SFR page to Page 1.
PnS
– Port n Schmitt Triggered Input
Register
SFR Address
Reset Value
P0S
B1H, Page 1
0000_0000 b
P1S
83H, Page 1
0000_0000 b
P3S
ACH, Page 1
0000_0000 b
7
6
5
4
3
2
1
0
PnS.7
PnS.6
PnS.5
PnS.4
PnS.3
PnS.2
PnS.1
PnS.0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Bit
Name
Description
7:0
PnS[7:0]
P0 Schmitt triggered input
0 = TTL level input of Pn.x.
1 = Schmitt triggered input of Pn.x.
P2S
– P20 Setting and Timer01 Output Enable
Regiser
Address
Reset Value
P2S
B5H, all pages
0000_0000 b
7
6
5
4
3
2
1
0
P20UP
-
-
-
T1OE
T0OE
-
P2S.0
R/W
-
-
-
R/W
R/W
-
R/W
Bit
Name
Description
7
P20UP
P2.0 pull-up enable
0 = P2.0 pull-up Disabled.
1 = P2.0 pull-up Enabled.
This bit is valid only when RPD (CONFIG0.2) is programmed as 0. When selecting as a
̅̅̅̅̅̅̅̅̅̅̅
pin, the pull-up is always enabled.