MC9RS08KA2 Datasheet, PDF (20/132 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 2 Pins and Connections
cables and the absolute value of the internal pullup device play almost no role in determining rise and fall
times on the BKGD pin.
2.4.4 General-Purpose I/O and Peripheral Ports
The remaining pins are shared among general-purpose I/O and on-chip peripheral functions such as timers
and analog comparator. Immediately after reset, all of these pins are configured as high-impedance
general-purpose inputs with internal pullup/pulldown devices disabled.
NOTE
To avoid extra current drain from floating input pins, the reset initialization
routine in the application program should either enable on-chip
pullup/pulldown devices or change the direction of unused pins to outputs.
Table 2-1. Pin Sharing Reference
Pin Name Direction Pullup/Pulldown¹
Alternative Functions²
V_DD
—
V_SS
—
PTA0
I/O
—
—
SWC
PTA0
KBIP0
ACMP+
Power
Ground
General-purpose input/output (GPIO)
Keyboard interrupt (stop/wait wakeup only)
Analog comparator input
PTA1
I/O
SWC
PTA1
KBIP1
ACMP-
General-purpose input/output (GPIO)
Keyboard interrupt (stop/wait wakeup only)
Analog comparator input
PTA2
I
PTA3
I/O³
SWC⁴
—⁴
PTA2
KBIP2
TCLK
RESET
V_PP
PTA3
ACMPO
BKGD
MS
General-purpose input
Keyboard interrupt (stop/wait wakeup only)
Modulo timer clock source
Reset
V_PP
General-purpose output
Analog comparator output
Background debug data
Mode select
PTA4⁵
I/O
SWC
PTA4
KBIP4
General-purpose input/output (GPIO)
Keyboard interrupt (stop/wait wakeup only)
PTA5⁵
I/O
SWC
PTA5
KBIP5
General-purpose input/output (GPIO)
Keyboard interrupt (stop/wait wakeup only)
1 _{SWC is software-controlled pullup/pulldown resistor; the register is associated with the respective port.}
2 _{Alternative functions are listed lowest priority first. For example, GPIO is the lowest priority alternative function of the}
PTA0 pin; ACMP+ is the highest priority alternative function of the PTA0 pin.
3 _{Output-only when configured as PTA3 function.}
4 _{When PTA2 or PTA3 is configured as RESET or BKGD/MS, respectively, pullup is enabled. When VPP is attached,}
pullup/pulldown is disabled automatically.
5 _{This pin is not available in 6-pin package. Enabling either the pullup or pulldown device is recommended to prevent extra}
current leakage from the floating input pin.
MC9RS08KA2 Series Data Sheet, Rev. 2
20
Freescale Semiconductor