Clock Select Header (W1) - Motorola M68MPB916R1 User Manual

HARDWARE PREPARATION AND INSTALLATION
Table 2-2. MPB Jumper Header Descriptions (continued)
1 2 3 Jumper installed on pins 1 and 2 (factory default); selects the MCU-internal
W5
phase-lock-loop frequency synthesizer as the system clock.
Jumper installed on pins 2 and 3; selects the EXTAL input as the system clock.
The MCU-internal phase-lock-loop frequency synthesizer is disabled.
Jumper installed on pins 1 and 2 (factory default); selects an MC68HC916R1
W6 1 2 3
MCU as the MCU type for this MPB.
Jumper installed on pins 2 and 3; selects an MC68HC16R1 MCU as the MCU
type for this MPB.
2.2.1

Clock Select Header (W1)

Jumper header W1 connects the MCU external clock (EXTAL) pin to either an
on-board or external (target-system) clock source. The drawing below shows the
factory configuration: a fabricated jumper on pins 1 and 2. This configuration
selects the MPB on-board clock source; crystal oscillator in the Y1 socket. (This
crystal provides for operation at the maximum rate the MCU allows via the
internal phase-locked loop or direct clock input.)
If you install the MPB in the active probe or directly on a target system, and use
the target system clock as the MPB clock, move the fabricated jumper to W1 pins
2 and 3. This connects the MCU EXTAL pin to the MAPI bus input pin. The
frequency of the external clock signal can be from 32 KHz to 16.78 MHz (or to
the maximum the MCU allows).
You cannot drive the MPB clock circuit from an external source
(target system) with a discrete crystal. If you use a target system
clock source to drive the MPB clock circuit, always use a logic-
driven clock such as a hybrid oscillator.
2-4
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
W1
1
2
3
NOTE
M68MPB16R1UM/D