Extended Temperature 82439TX (MTXC) Datasheet
34
PRELIMINARY
3.1.18.
DRAMEC
DRAM EXTENDED CONTROL REGISTER
Address Offset:
Default Value:
Access:
56h
52h
Read/Write
This 8-bit register contains additional controls for main memory DRAM operating modes and features.
Bit
Description
7
Reserved.
6
Refresh RAS# Assertion(RRA).
1=5 clocks (RAS# asserted for Refresh cycles). 0=4 clocks.
5
Fast EDO Lead Off (FELO).
1=Enables fast timing EDO read cycles. 0=Disable. This is valid for
EDO DRAMs only (in both a synchronous cache and a Cacheless system). This result is a 1
HCLK pull-in for all read leadoff latencies for EDO DRAMs. (i.e., Page hits, Page misses, and
Row Misses). This bit must be 0 if any of the DRAM rows is populated with FPM DRAMs.
4
Speculative Lead Off (SLD).
If set to 0, the DRAM Controller read request is presented before
the final memory target (Cache/DRAM/PCI) has been decoded by the MTXC. This results in a 1
HCLK pull-in for all read leadoff latencies. Note that if the cycle does not actually target DRAM,
the DRAM cycle is later terminated. The SLD bit applies to EDO/FPM and SDRAM
.
This bit
should be set to 1 in systems with a L2 cache and to 0 for systems without a L2 cache
3
Reserved.
2:1
Memory Address Drive Strength (MAD).
This field controls the strength of the output buffers
driving the MA, SRASx#, SCASx#, MWEx# and CKEx pins. It is recommended that series
termination or undershoot and overshoot diodes be used on these lines.
Bit[2:1]
MA[13,11:0], BA1
SRAS[A,B],SCAS[A,B],
MWEx#, CKEx
10 mA
16 mA
10 mA
16 mA
00
01
10
11
10 mA
10 mA
16 mA
16 mA
Setting Memory Address Drive Strength:
1 Row
00
* Assuming All Rows are buffered
2 Row
00
3 Row
11
4 Row
11
5 Row
11
6 Row
01*
0
Reserved.