ELANSC310 AMD [Advanced Micro Devices], ELANSC310 Datasheet - Page 44

• Manufacturer Part Number: ELANSC310
• Description: Single-Chip, 32-Bit, PC/AT Microcontroller
• Manufacturer: AMD [Advanced Micro Devices]

In the PLL Block Diagram, the INT_PLL is the Interme-
diate PLL, and is used to multiply the 32.768-kHz input
frequency by 45 to produce a 1.4746-MHz input for use
by the LS_PLL and the VID_PLL. The LS_PLL, or Low-
Speed PLL, is used to again multiply the 1.4746-MHz
input by 25 to produce a 36.864-MHz output. This out-
put of the LS_PLL is then divided down to provide the
frequencies shown in Table 20.
The LS_PLL also generates a 2.048-MHz signal used
by the VID_PLL or Video PLL to generate the 14.336-
MHz clock. This frequency is also available on the
X1OUT pin for use by an external video controller if se-
lected. This frequency should only be used to drive an
LCD panel.
The HS_PLL can be programmed to provide one of the
high-speed CPU clock frequencies shown in Table 19.
ÉlanSC310 Microcontroller
Power Management
Dynamic CPU clock switching is the primary form of
power management in the ÉlanSC310 microcontroller.
When the system is in the High-Speed PLL mode, the
ÉlanSC310 microcontroller can be configured to use
the High-Speed clock output of the PLL for main mem-
ory, local bus accesses, CPU idle cycles, and ROM
accesses configured to use the High-Speed clock. Dur-
ing cycles to I/O devices, ROM and other external ISA
devices, the CPU clock is dynamically switched to the
output of the Low-Speed PLL.
44
INT_PLL
LS_PLL
HS_PLL
VID_PLL
2 x CPU Frequency
Table 19. High-Speed CPU Clock Frequencies
Phase-Locked Loops
40 MHz
50 MHz
66 MHz
HS_PLL Output Frequency
1.4746 MHz
1.8432 MHz
1.1892 MHz
or 65.829 MHz
36.864 MHz
39.496 MHz, 50.023 MHz,
14.336 MHz
39.496 MHz
50.023 MHz
65.829 MHz
Élan™SC310 Microcontroller Data Sheet
Frequency
P R E L I M I N A R Y
Table 20. PLL Output
LS_PLL and VID_PLL
Divide by 2
16450 UART clock
8254 Timer clock
Input to high speed/low speed MUX
External video controller, if using an LCD panel
During operation in Low-Speed PLL mode, the CPU
clock is driven from Low-Speed clock output of the
Low-Speed PLL divide chain. The CPU clock fre-
quency used during Low Speed mode is programma-
ble to the following frequencies: 4.608 MHz, 2.304
MHz, 1.152 MHz, and 0.567 MHz. During Doze, Sleep,
and Suspend modes of operation, the CPU clock is
normally stopped. This clock operates at 9.216 MHz
when it is running.
Slow-refresh and self-refresh DRAMs are supported by
the ÉlanSC310 microcontroller. The refresh timer
source and the refresh rate are selectable. When the
CPU clock is stopped, the only clock source for refresh
is the 32-kHz clock. CAS-before-RAS DRAM refresh is
performed.
When the DMA subsystem is idle, the DMA clock con-
trol logic stops the clock input to the DMA controllers.
The DMA clock is started whenever any of the DREQ
inputs go High. When the DMA cycle is in progress, the
DMA clock remains active as long as a DREQ input is
High or the internal AEN signal is active.
To reduce power consumption in Doze, Sleep, and
Suspend modes, the CPU clock is turned off. To further
reduce the power consumption in these three modes,
the High-Speed PLL is shut off. The Low-Speed PLL is
left on by default, but can be programmed to turn off in
all three modes.
For information about the signals associated with
power management (ACIN, BL4–BL1, EXTSMI, LPH,
PGP3–PGP0, PMC4–PMC0, and SUS/RES), see
“Power Management Interface” on page 34. For more
information, see Chapter 1 of the Élan
controller Programmer’s Reference Manual , order
#20665.
Where Used
TM
SC310 Micro-