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2.5.7 Suspend to DRM
Power-on-suspend (POS), Suspend-to-RAM (STR) and Suspend-to-Disk (STD) or so called Soft-off are three different suspend
states supported by the VT82C686A. These suspend functions are implemented not only in a notebook PC design but also in a
desktop PC design. And the STR function is specially described in this section.
2.5.7.1 Suspend DRAM Refresh
During STR state, power is removed from most of the system except the system DRAM and the power management section of
VT82C686A.
Power is supplied to the suspend refresh logic of the VT82C694X (VSUS) and the suspend logic of the
VT82C686A (VCCSUS). One additional suspend status indicator (SUSST1#) is provided to inform the north bridge and the rest
of the system of the processor and system suspend states. SUSST1# is asserted to tell the north bridge to switch to "Suspend
DRAM Refresh" mode. SUSST1# is asserted when the system enters the suspend state or the processor enters the suspend (C3)
state. SUSST1# is connected to the north bridge to switch between normal and suspend-DRAM-refresh modes The Suspend
DRAM Refresh application circuit is shown in Figure 2-62.
VT82C694X
(North Bridge)
CKE0/FENA
CKE1/GCKE#
CKE2/CSB6#
CKE3/CSB7#
CKE4/CSA6#
CKE5/CSA#
Notes:
1. During STR state, all VT82C694X and VT82C686A signals are powered by 3.3V suspend power.
2. Main memory is also powered by 3.3V suspend power through V_DIMM.
Suspend DRAM refresh state (self refresh mode for DRAM modules) is entered by having CKE[0:5], SRAS[A:B}#, SCAS[A:B]#
held low with SW[A:B]# high at the rising edge of the SDRAM clock.
Preliminary Revision 0.5, November 19, 1999
AC22
AF23
AE24
AD23
AF164
SRASA#
AF12
SCASA#
AE12
SWEA#
AC23
AF24
AA17
SRASB#
AB13
SCASB#
AC12
SWEB#
3V3SB
AC4
VSUS
AD4
SUSSAT#
Figure 2-62. Suspend DRAM Refresh Application Circuit
Design Guide - VT82C694X Apollo Pro133 with VT82C686A
Main Memory
128
DIMM1
63
(Group A)
115
111
27
48
128
DIMM2
63
(Group A)
115
111
27
48
128
DIMM3
63
(Group B)
115
111
27
48
3V3SB
VT82C686A
(South Bridge)
10K
ohm
T17
SUSST1
70
V_DIMM
V_DIMM
V_DIMM
V_DIMM
3V3SB
R16
VCCSUS
L16
VCCSUS
Motherboard Design Guidelines
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