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GT-96100A Advanced Communication Controller
106
Revision 1.0
5.2
Connecting the Address Bus to the SDRAM
Connecting the address bus to SDRAM is very simple with The GT-96100A. The SDRAM controller has its own
address bus and its depends on whether a 16 Mbit or 64 Mbit SDRAMs are being used.
5.2.1
16 MBit SDRAMs
For 16 Mbit SDRAMs, DAdr[10:0] and BankSel[0] are outputs of the GT-96100A and must be directly con-
nected to address bits 10-0 and Bank Select of the actual SDRAM.
NOTE: DAdr[11] and BankSel[1] are not used when connecting to 16 Mbit SDRAMs. These lines are in HIGH-
Z state when accessing 16Mbit SDRAMs.
During a SRAS cycle, a valid row address is placed on the DAdr[10:0] and BankSel[0] lines. During the SCAS
cycle, a valid column address is placed on DAdr[9:0] (10-bit). DAdr[10] is used as the auto-precharge select bit
and is always written 0 during SCAS cycles. BankSel[0] is held constant from the SRAS cycle.
With 16 MBit SDRAMs, the GT-96100A supports a maximum of 4M addresses, 12 address bits for SRAS and 10
address bits for SCAS.
5.2.2
64/128 Mbit SDRAMs
For 64/128 MBit SDRAMs, DAdr[11:0] and BankSel[1:0] are outputs of the GT-96100A and must be directly
connected to address bits 11-0 and Bank Select of the actual SDRAM.
During a SRAS cycle, a valid row address is placed on the DAdr[11:0] and BankSel lines. During the SCAS
cycle, a valid column address is placed on DAdr[11,9:0] (11-bit). DAdr[10] is used as the auto-precharge select
bit and is always written 0 during SCAS cycles. BankSel is held constant from the SRAS cycle.
With 64 MBit SDRAMs, the GT-96100A supports a maximum of 16M addresses, 14 address bits for SRAS and
10 address bits for SCAS (DAdr[11] is ignored and is in HIGH-Z state when accessing 64 Mbit SDRAMs).
Table 76: SysAD/PCI Address Decoding for 64-bit SDRAM, 256 Mbit
Ad drDeco de,
0x47c
SysAD/PCI Bits used fo r
SRAS* o n Ban kSel[0],
BankSel[1], DAdr[12:0]
SysAD/PCI Bits used fo r
SCAS* o n Ban kSel[0],
BankSel[1], DAdr[12:0]
000
Illegal setting for 64, 128Mbit and 256Mbit SDRAM
001
6, 7, 25-13
6, 7, 29-28, “0”, 27-26, 12-8, 5-3
010
11, 12, 25-13
11, 12, 29-28, “0”, 27-26, 10-3
011
13, 14, 25-15, 12-11
13, 14, 29-28, “0”, 27-26, 10-3
100
21, 22, 25-23, 20-11
21, 22, 29-28, “0”, 27-26, 10-3
101
23, 24, 25, 22-11
23, 24, 29-28, “0”, 27-26, 10-3
110
24, 25, 23-11
24, 25, 29-28, “0”, 27-26, 10-3
111
25, 26, 27, 22-11
25, 26, 29-28, “0”, 24-23, 10-3