SC3200 datasheet(18/447 Pages) AMD

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AMD Geode™ SC3200 Processor Data Book

Architecture Overview

Revision 5.1

Table 2-1. SC3200 Memory Controller Register Summary

GX_BASE+

Memory Offset

Width

(Bits)

Type

Name/Function

Reset Value

8400h-8403h

R/W

MC_MEM_CNTRL1. Memory Controller Control Register 1

248C0040h

8404h-8407h

R/W

MC_MEM_CNTRL2. Memory Controller Control Register 2

00000801h

8408h-840Bh

R/W

MC_BANK_CFG. Memory Controller Bank Configuration

41104110h

840Ch-840Fh

R/W

MC_SYNC_TIM1. Memory Controller Synchronous Timing

2A733225h

8414h-8417h

R/W

MC_GBASE_ADD. Memory Controller Graphics Base

Address Register

00000000h

8418h-841Bh

R/W

MC_DR_ADD. Memory Controller Dirty RAM Address

00000000h

841Ch-841Fh

R/W

MC_DR_ACC. Memory Controller Dirty RAM Access

0000000xh

Table 2-2. SC3200 Memory Controller Registers

Bit

Description

GX_BASE+ 8400h-8403h

MC_MEM_CNTRL1 (R/W)

Reset Value: 248C0040h

31:30

MDCTL (MD[63:0] Drive Strength). 11 is strongest, 00 is weakest.

RSVD (Reserved) Write as 0.

28:27

MABACTL (MA[12:0] and BA[1:0] Drive Strength). 11 is strongest, 00 is weakest.

RSVD (Reserved). Write as 0.

25:24

MEMCTL (RASA#, CASA#, WEA#, CS[1:0]#, CKEA, DQM[7:0] Drive Strength). 11 is strongest, 00 is weakest.

23:22

RSVD (Reserved). Write as 0.

RSVD (Reserved). Must be written as 0. Wait state on the X-Bus x_data during read cycles - for debug only.

20:18

SDCLKRATE (SDRAM Clock Ratio). Selects SDRAM clock ratio.

000: Reserved

100: ÷ 3.5

001: ÷ 2

101: ÷ 4

010: ÷ 2.5

110: ÷ 4.5

011: ÷ 3 (Default)

111: ÷ 5

Ratio does not take effect until the SDCLKSTRT bit (bit 17 of this register) transitions from 0 to 1.

SDCLKSTRT (Start SDCLK). Start operating SDCLK using the new ratio and shift value (selected in bits [20:18] of this reg-

ister).

0: Clear.

1: Enable.

This bit must transition from zero (written to zero) to one (written to one) in order to start SDCLK or to change the shift value.

16:8

RFSHRATE (Refresh Interval). This field determines the number of processor core clocks multiplied by 64 between refresh

cycles to the DRAM. By default, the refresh interval is 00h. Refresh is turned off by default.

7:6

RFSHSTAG (Refresh Staggering). This field determines number of clocks between the RFSH commands to each of the

four banks during refresh cycles:

00: 0 SDRAM clocks

01: 1 SDRAM clocks (Default)

10: 2 SDRAM clocks

11: 4 SDRAM clocks

Staggering is used to help reduce power spikes during refresh by refreshing one bank at a time. If only one bank is installed,

this field must be written as 00.

2CLKADDR (Two Clock Address Setup). Assert memory address for one extra clock before CS# is asserted.

0: Disable.

1: Enable.

This can be used to compensate for address setup at high frequencies and/or high loads.

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