Freescale Semiconductor, Inc.
Pinout and Signal Descriptions
3.5.15 Port Pull-Up Pull-Down and Reduced Drive
MCU ports can be configured for internal pull-up. 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 3-4 summarizes the port pull-up/pull-
down default status and controls.
Table 3-4. Port Pull-Up, Pull-Down and Reduced Drive Summary
Enable Bit
Reduced Drive Control Bit
Port
Name
Resistive
Input Loads
Register
(Address)
Reset
State
Register
(Address)
Reset
State
Bit Name
Bit Name
Port A
Port B
Pull-up
Pull-up
PUCR ($000C)
PUCR ($000C)
PUPA
PUPB
Disabled RDRIV ($000D)
Disabled RDRIV ($000D)
RDPA
RDPB
Full drive
Full drive
Port E:
PE7, PE[3:2]
PE[1:0]
Pull-up
Pull-up
None
PUCR ($000C)
PUCR ($000C)
PUPE
PUPE
Enabled RDRIV ($000D)
Enabled
RDPE
—
Full drive
PE[6:4]
—
RDRIV ($000D)
RDPE
Full drive
Full drive
Pull-up or
Pull-down
Port H
Port J
PUCR ($000C)
PUCR ($000C)
PUPH
PUPJ
Disabled RDRIV ($000D)
Disabled RDRIV ($000D)
RDPH
RDPJ
Pull-up or
Pull-down
Full drive
Port K
Port P
Pull-up
Pull-up
Pull-up
Pull-up
Pull-up
Pull-up
None
PUCR ($000C)
PWCTL ($0054)
SP0CR2 ($00D1)
TMSK2 ($008D)
IBPURD ($00E5)
PUPK
PUPP
PUPS
TPU
Disabled RDRIV ($000D)
Disabled PWCTL ($0054)
RDPK
RDPP
Full drive
Full drive
Full drive
Full drive
Full drive
Full drive
Port S
Enabled SP0CR2 ($00D1) RDPS
Disabled TMSK2 ($008D) TDRB
Port T
Port IB[7:4]
Port IB[3:2]
Port AD0
PUPIB Disabled IBPURD ($00E5) RDPIB
Always enabled when pins are input
IBPURD ($00E5) RDPIB
—
—
—
—
—
—
—
Port AD1
None
—
Port CAN1[1]
Port CAN1[0]
Port CAN0[1]
Port CAN0[0]
None
—
Pull-up
None
Always enabled
—
Pull-up
Always enabled
Technical Data
MC68HC912DG128 — Rev 3.0
Pinout and Signal Descriptions
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