
Chapter 6 Parallel Input/Output
MC9S08GB/GT Data Sheet, Rev. 2.3
82
Freescale Semiconductor
6.3.6
Port F and High-Current Drivers
Figure 6-7. Port F Pin Names
Port F is an 8-bit port general-purpose I/O that is not shared with any peripheral module. Port F has high
current output drivers.
Port F pins are available as general-purpose I/O pins controlled by the port F data (PTFD), data direction
(PTFDD), pullup enable (PTFPE), and slew rate control (PTFSE) registers. Refer to
Section 6.4, “Parallel
I/O Controls
”
for more information about general-purpose I/O control.
6.3.7
Port G, BKGD/MS, and Oscillator
Figure 6-8. Port G Pin Names
Port G is an 8-bit port which is shared among the background/mode select function, oscillator, and
general-purpose I/O. When the background/mode select function or oscillator is enabled, the pin direction
will be controlled by the module function.
Port G pins are available as general-purpose I/O pins controlled by the port G data (PTGD), data direction
(PTGDD),pullupenable(PTGPE),andslewratecontrol(PTGSE)registers.Referto
Section 6.4,“Parallel
I/O Controls
”
for more information about general-purpose I/O control.
The internal pullup for PTG0 is enabled when the background/mode select function is enabled, regardless
of the state of PTGPE0. During reset, the BKGD/MS pin functions as a mode select pin. After the MCU
is out of reset, the BKGD/MS pin becomes the background communications input/output pin. The PTG0
can be configured to be a general-purpose output pin. Refer to
Chapter 3, “Modes of Operation
”,
Chapter 5, “Resets, Interrupts, and System Configuration
”
, and
Chapter 15, “Development Support
” for
more information about using this pin.
The ICG module can be configured to use PTG2–PTG1 ports as crystal oscillator or external clock pins.
Refer to
Chapter 13, “Inter-Integrated Circuit (IIC) Module
” for more information about using these pins
as oscillator pins.
6.4
Parallel I/O Controls
Provided no on-chip peripheral is controlling a port pin, the pins operate as general-purpose I/O pins that
are accessed and controlled by a data register (PTxD), a data direction register (PTxDD), a pullup enable
register (PTxPE), and a slew rate control register (PTxSE) where x is A, B, C, D, E, F, or G.
Port F
Bit 7
6
5
4
3
2
1
Bit 0
MCU Pin:
PTF7
PTF6
PTF5
PTF4
PTF3
PTF2
PTF1
PTF0
Port G
Bit 7
6
5
4
3
2
1
Bit 0
MCU Pin:
PTG7
PTG6
PTG5
PTG4
PTG3
PTG2/
EXTAL
PTG1/
XTAL
PTG0/
BKGD/MS