
AMD Geode SC1200/SC1201 Processor Data Book
171
Core Logic Module
Revision 7.1
6.2.5.6
ROM Interface
The Core Logic module positively decodes memory
addresses
000F0000h-000FFFFFh
(64
KB)
and
FFFC0000h-FFFFFFFFh (256 KB) at reset. These memory
cycles cause the Core Logic module to claim the cycle, and
generate an ISA bus memory cycle with ROMCS#
asserted. The Core Logic module can also be configured to
respond to memory addresses FF000000h-FFFFFFFFh
(16 MB) and 000E0000h-000FFFFFh (128 KB).
8- or 16-bit wide ROM is supported. BOOT16 strap deter-
mines the width after reset. MCR[14,3] (Offset 34h) in the
bit details) allows program control of the width.
Flash ROM is supported in the Core Logic module by
enabling the ROMCS# signal on write accesses to the
ROM region. Normally only read cycles are passed to the
ISA bus, and the ROMCS# signal is suppressed for write
cycles. When the ROM Write Enable bit (F0 Index 52h[1])
is set, a write access to the ROM address region causes a
write cycle to occur with MEMW#, WR# and ROMCS#
asserted.
6.2.5.7
PCI and Sub-ISA Signal Cycle Multiplexing
The SC1200/SC1201 processor multiplexes most PCI and
Sub-ISA signals on the balls listed in
Table 6-3, in order to
reduce the number of balls on the device. Cycle multiplex-
page 172), where the internal Core Logic PCI bridge arbi-
trates between PCI cycles and Sub-ISA cycles. Other PCI
and Sub-ISA signals remain non-shared, however, some
Sub-ISA signals may be muxed with GPIO.
Sub-ISA cycles are only generated as a result of GX1 mod-
ule accesses to the following addresses or conditions:
ROMCS# address range.
DOCCS# address range.
IOCS0# address range.
IOCS1# address range.
An I/O write to address 80h or to 84h.
Internal ISA is programmed to be the subtractive decode
agent and no other agents claim the cycle.
If the Sub-ISA and PCI bus have more than four compo-
nents, the Sub-ISA components can be buffered using
74HCT245 or 74FCT245 type transceivers. The RD# (an
AND of IOR#, MEMR#) signal can be used as DIR control
while TRDE# is used as enable control.
Table 6-3. Cycle Multiplexed PCI / Sub-ISA Balls
PCI
Sub-ISA
Ball No.
EBGA
TEPBGA
AD0
A0
A17
U1
AD1
A1
D16
P3
AD2
A2
A18
U3
AD3
A3
A15
N1
AD4
A4
A16
P1
AD5
A5
A14
N3
AD6
A6
C15
N2
AD7
A7
B14
M2
AD8
A8
C14
M4
AD9
A9
B13
L2
AD10
A10
C13
L3
AD11
A11
C12
K1
AD12
A12
L4
AD13
A13
C11
J1
AD14
A14
A11
K4
AD15
A15
B10
J3
AD16
A16
A7
E1
AD17
A17
C7
F4
AD18
A18
D7
E3
AD19
A19
A6
E2
AD20
A20
D6
D3
AD21
A21
C6
D1
AD22
A22
A5
D2
AD23
A23
F4
B6
AD24
D0
C5
C2
AD25
D1
D5
C4
AD26
D2
A4
C1
AD27
D3
B4
D4
AD28
D4
C4
B4
AD29
D5
A3
B3
AD30
D6
C2
A3
AD31
D7
B3
D5
C/BE0#
D8
A13
L1
C/BE1#
D9
A10
J2
C/BE2#
D10
D8
F3
C/BE3#
D11
A8
H4
PAR
D12
C10
J4
TRDY#
D13
B8
F1
IRDY#
D14
C8
F2
STOP#
D15
D9
G1
DEVSEL#
BHE#
B5
E4