MC81F4x16
10.4 R3 Port Registers
R3CONH – R33~R35
R3 PORT CONTROL HIGH REGISTER
00DCH
A reset clears the R3CONH register to „00H‟, makes R35-R33 pins input mode. You can use
R3CONH register setting to select input or output mode (open-drain or push-pull) and enable
alternative functions.
7
6
5
4
3
2
1
0
–
–
R35
R34
R33
R3CONH
Reset value: 00H
–
–
R/W
R/W
R/W
R/W
R/W
R/W
–
bit7 – bit6
Not used for MC81F4x16
00: Schmitt trigger input mode
01: Not available
R35
R35/RESETB ( *note* )
R34/Xin ( *note* )
10: Output mode, open-drain
11: Not available
00: Schmitt trigger input mode
01: Schmitt trigger input pull-up mode
10: Output mode, open-drain
11: Output mode, push-pull
00: Schmitt trigger input mode
01: Schmitt trigger input pull-up mode
10: Output mode, open-drain
11: Output mode, push-pull
R34
R33
R33/Xout ( *note* )
Note :
If you want to use RESETB, the LVREN (ROM OPTION [7]) must select to LVR disable
mode („1‟). If you want to use R35, the LVREN (ROM OPTION [7]) must be selected to LVR
enable mode („0‟).
If you want to use XIN and XOUT, the OSCS (ROM OPTION [2:0]) must select to
Crystal/ceramic oscillator mode (111b). If you want to use R33 and R34, the OSCS (ROM
OPTION [2:0]) must select to Internal RC mode (001b, 010b, 011b, 100b).
Even you are in case of using emulator you must select the ROM OPTION switch properly to
use those R33,R34,R35 ports.
October 19, 2009 Ver.1.35
85
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