Datasheet

Chapter 2 External Signal Description
MC9S08QG8 and MC9S08QG4 Data Sheet, Rev. 5
26 Freescale Semiconductor
Figure 2-4. Basic System Connections
2.2.1 Power
V
DD
and V
SS
are the primary power supply pins for the MCU. This voltage source supplies power to all
I/O buffer circuitry, ACMP and ADC modules, and to an internal voltage regulator. The internal voltage
regulator provides a regulated lower-voltage source to the CPU and other internal circuitry of the MCU.
Typically, application systems have two separate capacitors across the power pins: a bulk electrolytic
capacitor, such as a 10-μF tantalum capacitor, to provide bulk charge storage for the overall system, and a
bypass capacitor, such as a 0.1-μF ceramic capacitor, located as near to the MCU power pins as practical
to suppress high-frequency noise.
V
DD
V
SS
RESET/IRQ
OPTIONAL
MANUAL
RESET
PORT
A
V
DD
BACKGROUND HEADER
C
BY
0.1 μF
C
BLK
10 μF
+
3 V
+
SYSTEM
POWER
I/O AND
PERIPHERAL
INTERFACE TO
SYSTEM
APPLICATION
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
PTA1/KBIP1/ADP1/ACMP–
PTA2/KBIP2/SDA/ADP2
PTA3/KBIP3/SCL/ADP3
V
DD
PORT
B
PTA4/ACMPO/BKGD/MS
PTA5/IRQ
/TCLK/RESET
PTB0/KBIP4/RxD/ADP4
PTB1/KBIP5/TxD/ADP5
PTB2/KBIP6/SPSCK/ADP6
MC9S08QG8/4
PTB3/KBIP7/MOSI/ADP7
PTB4/MISO
PTB5/TPMCH1/SS
BKGD
PTB6/SDA/XTAL
PTB7/SCL/EXTAL
XTAL
EXTAL
C2
C1
X1
R
F
R
S
NOTE 1
NOTE 2
NOTES:
1. Not required if using the internal clock option.
2. XTAL is the same pin as PTB6; EXTAL the same pin as PTB7.
3. The RESET
pin can only be used to reset into user mode; you can not enter BDM using the RESET pin.
BDM can be entered by holding MS low during POR or writing a 1 to BDFR in SBDFR with MS low after
issuing the BDM command.
4. IRQ
feature has optional internal pullup device.
5. RC filter on RESET
/IRQ pin recommended for noisy environments.
ASYNCHRONOUS
INTERRUPT
INPUT
NOTE 2
V
DD
4.7 k Ω –10 k Ω
0.1 μ F