4- 18
MC68341 USER’S MANUAL
MOTOROLA
corresponding bits in the PPARB for a particular signal, the port B pins can be configured
for different pin functions. Upon reset, port B is configured as IRQ7–IRQ1, MODCK.
Table 4-6. Port B Pin Assignment Register
Pin Function
Signal
PPARB = 0
PPARB = 1
IRQ7
PORTB7
IRQ7
IRQ6
PORTB6
IRQ6
IRQ5
PORTB5
IRQ5
IRQ4
PORTB4
IRQ4
IRQ3
PORTB3
IRQ3
IRQ2
PORTB2
IRQ2
IRQ1
PORTB1
IRQ1
IRQ0
PORTB0
MODCK
NOTE: MODCK has no function after reset.
4.2.6 Low-Power Stop
Executing the LPSTOP instruction provides reduced power consumption when the
MC68341 is idle; only the SIM41 remains active. Operation of the SIM41 clock and
CLKOUT during LPSTOP is controlled by the STSIM and STEXT bits in the SYNCR (see
Table 4-3). LPSTOP disables the clock to the software watchdog in the low state. The
software watchdog remains stopped until the LPSTOP mode ends; it begins to run again
on the next rising clock edge.
NOTE
When the CPU32 executes the STOP instruction (as opposed
to LPSTOP), the software watchdog continues to run. If the
software watchdog is enabled, it issues a reset or interrupt
when timeout occurs.
The periodic interrupt timer and real time clock do not respond to an LPSTOP instruction;
thus, they can be used to exit LPSTOP as long as their interrupt request level is higher
than the CPU32 interrupt mask level. To stop the periodic interrupt timer while in LPSTOP,
the PITR must be loaded with a zero value before LPSTOP is executed. The bus monitor,
double bus fault monitor, and spurious interrupt monitor are all inactive during LPSTOP.
The STP bit in the MCR of each on-chip module (DMA, timer, and serial modules) should
be set prior to executing the LPSTOP instruction. Setting the STP bit stops all clocks
within each of the modules, except for the clock from the IMB. The clock from the IMB
remains active to allow the CPU32 access to the MCR of each module. The system clock
stops on the low phase of the clock and remains stopped until the STP bit is cleared by
the CPU32 or until reset. For more information, see the description of the MCR STP bit for
each module.
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
..
.