MC68LC302 Datasheet, PDF (28/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

Configuration, Clocking, Low Power Modes, and Internal Memory Map
LPM—Low Power Modes
When the 68000 core executes the STOP instruction, the IMP will enter the specified
mode.
LPM1–0:
00 = Normal - the IMP PLL and clock oscillator will continue to operate normally.
01 = Stand_by Mode
10 = DOZE Mode
11 = Stop Mode
2.4.4.1.7 Low Power Drive Control Register (LPDCR). This register controls the state of
the IMP’s 68000 address and data buses during the Standby, Doze, and Stop modes. By
programming this register it is possible to minimize power consumption due to external pul-
lups or pull downs, or floating inputs.
LPDCR
BAR+$82A
7
6
5
4
3
2
1
0
LPAL
LPDL
LPDEN
RESET:
0
0
0
0
0
0
0
0
Read/Write
LPDEN—Low Power Drive Enable
0 - The IMP 68000 data and address buses will be high impedance.
1 - The IMP 68000 data and address buses to be driven according to the LPDL bit.
LPDL—Low Power Drive Data Low
0 - The data bus will be driven high when the LPDEN bit is set.
1 - The data bus will be driven low when the LPDEN bit is set.
LPAL-Low Power Drive Address Low
0 - The address bus will be driven high when the LPDEN bit is set.
1 - The address bus will be driven low when the LPDEN bit is set.
2.4.4.1.8 IMP Power Down Register (IPWRD). The IPWRD is a 8-bit read/ write register
located at $0FB that is used to control the low power operation of the IMP. This register must
be written with the same operand as the STOP instruction that follows. This tells the hard-
ware what level of interrupt (and above) will stop the MC68LC302 from entering low power
if it occurs while the clocks are being stopped.
2.4.4.1.9 Default Operation Modes, See 2.4.2.1 Default System Clock Generation.
2.4.4.2 LOW POWER SUPPORT. The following sections describe how to enter the various
low power modes.
2.4.4.2.1 Enter the SLOW_GO mode. When the required IMP performance can be
achieved with a lower clock rate, the user can reduce power consumption by dividing IMP
MOTOROLA
MC68LC302 REFERENCE MANUAL
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