SC1100 datasheet(37/348 Pages) NSC

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Signal Definitions (Continued)

PCIRST#

M26

PCI and System Reset. PCIRST# is the reset signal for

the PCI bus and system. It is asserted for approximately

100 µs after POR# is negated.

---

2.4.2

Memory Interface Signals

Signal Name

Ball No.

Type

Description

Mux

MD[63:0]

See

Table 2-3

on page

I/O

Memory Data Bus. The data bus lines driven to/from

system memory.

---

MA[12:0]

See

Table 2-3

on page

Memory Address Bus. The multiplexed row/column

address lines driven to the system memory. Supports

256-Mbit SDRAM.

---

BA1

C12

Bank Address Bits. These bits are used to select the

component bank within the SDRAM.

---

BA0

C11

---

CS1#

Chip Selects. These bits are used to select the module

bank within system memory. Each chip select corre-

sponds to a specific module bank. If CS# is high, the

bank(s) do not respond to RAS#, CAS#, and WE# until

the bank is selected again.

---

CS0#

---

RASA#

Row Address Strobe. RAS#, CAS#, WE# and CKE are

encoded to support the different SDRAM commands.

RASA# is used with CS[1:0]#.

---

CASA#

Column Address Strobe. RAS#, CAS#, WE# and CKE

are encoded to support the different SDRAM commands.

CASA# is used with CS[1:0]#.

---

WEA#

Write Enable. RAS#, CAS#, WE# and CKE are encoded

to support the different SDRAM commands. WEA# is

used with CS[1:0]#.

---

DQM[7:0]

C15,

C14, N3,

P3, A11,

B11, M2,

Data Mask Control Bits. During memory read cycles,

these outputs control whether SDRAM output buffers are

driven on the MD bus or not. All DQM signals are

asserted during read cycles.

During memory write cycles, these outputs control

whether or not MD data is written into SDRAM.

DQM[7:0] connect directly to the [DQM7:0] pins of each

DIMM connector.

---

CKEA

A19

Clock Enable. These signals are used to enter Sus-

pend/power-down mode. CKEA is used with CS[1:0]#.

If CKE goes low when no read or write cycle is in

progress, the SDRAM enters power-down mode. To

ensure that SDRAM data remains valid, the self-refresh

command is executed. To exit this mode, and return to

normal operation, drive CKE high.

These signals should have an external pull-down resistor

of 33 K

Ω.

---

2.4.1

System Interface (Continued)

Signal Name

Ball No.

Type

Description

Mux

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