Datasheet

General Description
M68HC12B Family Data Sheet, Rev. 9.1
36 Freescale Semiconductor
1.6.5 Port Pullup, Pulldown, and Reduced Drive
MCU ports can be configured for internal pullup. To reduce power consumption and RFI, the pin output
drivers can be configured to operate at a reduced drive level. Reduced drive causes a slight increase in
transition time depending on loading and should be used only for ports which have a light loading. Table
1-5 summarizes the port pullup default status and controls.
Table 1-5. Port Pullup, Pulldown, and Reduced Drive Summary
Port
Name
Resistive
Input Loads
Enable Bit Reduced Drive Control Bit
Register
(Address)
Bit
Name
Reset
State
Register
(Address)
Bit
Name
Reset
State
Port A Pullup
PUCR
($000C)
PUPA Disabled
RDRIV
($000D)
RDPA Full drive
Port B Pullup
PUCR
($000C)
PUPB Disabled
RDRIV
($000D)
RDPB Full drive
Port E
PE7, PE3, PE2,
PE1, PE0
Pullup
PUCR
($000C)
PUPE Enabled
RDRIV
($000D)
RDPE Full drive
Port E
PE4
None —
RDRIV
($000D)
RDPE Full drive
Port E
PE6, PE5
Pulldown Enabled during reset — — —
Port P Pullup
PWCTL
($0054)
PUPP Disabled
PWCTL
($0054)
RDPP Full drive
Port S
PS1–PS0
Pullup
PURDS
($00DB)
PUPS0 Disabled
PURDS
($00DB)
RDPS0 Full drive
Port S
PS3–PS2
Pullup
PURDS
($00DB)
PUPS1 Disabled
PURDS
($00DB)
RDPS1 Full drive
Port S
PS7–PS4
Pullup
PURDS
($00DB)
PUPS2 Disabled
PURDS
($00DB)
RDPS2 Full drive
Port T Pullup
TMSK2
($008D)
PUPT Disabled
TMSK2
($008D)
RDPT Full drive
Port DLC/PCAN
(1)
1. Port DLC applies to the MC68HC912B32 and MC68HC12BE32 and PCAN to the MC68HC(9)12BC32.
Pullup
DLCSCR
($00FD)
DLCPUE Disabled
DLCSCR
($00FD)
DLCRDV Full drive
Port AD None — —
BKGD Pullup — — Enabled — — Full drive