21285-AB

Manufacturer Part Number21285-AB
DescriptionMicroprocessor, 21285 Core Logic For SA-110 Microprocessor
ManufacturerIntel Corporation
21285-AB datasheet
 

Specifications of 21285-AB

CaseBGADc99+/00+
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SDRAM Addresses

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SDRAM and ROM Operation
Mode register set is generated in response to an SA-110 write to a specified address space (see
Section
5.1.1). The mode register of the SDRAMs must be written before any SDRAM writes or
reads can be done. The mode register burst length field (bits [2:0]) must be written to a value of 2h
to indicate a burst size of four, and the burst type field (bit [3]) must be written to a value of 0h to
indicate sequential burst.
Memory reads and writes are done in bursts of four Dwords. For a read that requires less than four
Dwords (for example, a memory read from PCI), the 21285 discards the unused data. For a write
that requires less than four Dwords, the 21285 uses the dqm pins to inhibit writing to some
Dwords. The dqm pins also inhibit writing to unoccupied bytes.
sizes. The row/column multiplexer mode is the value programmed into the SDRAM address and
size register (see
Section
Table 4-1. Array Sizes
SDRAM Type
Banks
Depth
2
128K
2
256K
2
512K
2
1M
2
2M
2
1M
4
512K
2
2M
4
1M
2
4M
4
2M
2
8M
4
4M
4.1.1

SDRAM Addresses

The SDRAM addresses are driven on the ma[12:0] bits. In
equal to bits [23:21], [18:9] of the address being accessed, however, some SDRAMs do not use all
of the addresses. The column address is determined by the address multiplexer mode field of the
SDRAM address and size register for the selected array. The array selection is based on bits
[27:20] of the address (see
(indicating that it is an A[20:19] where A[20] may not be used) during both row and column time.
4-2
7.3.13).
Address Bits
SDRAMs
Width
Bank
Row
Col.
in Array
8Mb Parts
32
1
9
8
1
16Mb Parts
32
1
10
8
1
16
1
11
8
2
8
1
11
9
4
4
1
11
10
8
64Mb Parts
32
1
12
8
1
32
2
11
8
1
16
1
13
8
2
16
2
12
8
2
8
1
13
9
4
8
2
12
9
4
4
1
13
10
8
4
2
12
10
8
Section
7.3.13). The SDRAM bank address is driven on ba[1:0]
Table 4-1
lists the available array
Array
Row/Column
Size
Multiplexer Mode
1MB
000
2MB
000
4MB
001
8MB
001
16MB
001
8MB
010
8MB
011
16MB
010
16MB
100
32MB
010
32MB
100
64MB
010
64MB
100
Table
4-2, the row address is always
21285 Core Logic for SA-110 Datasheet