Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
April 30, 1998
1.4
PIN DESCRIPTIONS
The following paragraphs give a description of each functional pin.
1.4.1 VDD, VSS
Power is supplied to the MCU using these pins. VDD is the positive supply and
VSS is the ground pin.
1.4.2 OSC1, OSC2
OSC2 is only available on MC68HC05PL4B.
The OSC1 and OSC2 pins are the connections for the on-chip oscillator — the
following con gur ations are available:
1. A crystal or ceramic resonator as shown in Figure 1-4(a).
2. An external clock signal as shown in Figure 1-4(b).
The external oscillator clock frequency, f
, is divided by two to produce the
OSC
internal operating frequency, f .
OP
MCU
MCU
2 M
Ω
OSC1
OSC2
OSC1
OSC2
UNCONNECTED
EXTERNAL CLOCK
(a) Crystal or
(c) External
Clock Source
Connection
Ceramic Resonator
Connections
Figure 1-4. Oscillator Connections
1.4.3 RESET
This active low input-only pin is used to reset the MCU to a known start-up state.
The RESET pin has an Schmitt trigger circuit as part of its input to improve noise
immunity.
1.4.4 LED/IRQ
This pin has two functions, con gured b y the IRQEN bit in the Miscellaneous Con-
trol and Status Register, at $1C (MISCR).
When this pin is IRQ, it drives the asynchronous IRQ interrupt function of the
CPU. The IRQ interrupt function uses the IRQS bit in the MISCR to provide either
only negative edge-sensitive triggering or both negative edge-sensitive and low
level-sensitive triggering. If the MISCR bit is set to enable level-sensitive
GENERAL DESCRIPTION
MC68HC05PL4
REV 2.0
1-4
For More Information On This Product,
Go to: www.freescale.com
FREESCALE [ Freescale ]
