SDRAM Controller
10-12
Élan™SC520 Microcontroller User’s Manual
During read-modify-write cycles, the SDRAM burst read portion of the transaction is
terminated early by the write cycle. This is independent of the enable state of the read-
ahead feature of the read buffer, which is provided to increase read performance by
prefetching data from SDRAM. See “Buffering” on page 10-17 for more information on the
read buffer and associated read-ahead feature.
Write requests to SDRAM always occur as single data transfers, regardless of the amount
of data written by a master. When the write buffer is enabled, all write transactions to SDRAM
are initiated by the write buffer. The write buffer features write merging, write collapsing
and read merging. See “Buffering” on page 10-17 for more information on the write buffer.
10.5.2
SDRAM Addressing
The ÉlanSC520 microcontroller asserts one of the four chip select signals, SCS3–SCS0,
during access to one of the four memory banks. Table 10-7 shows the SDRAM memory
address as a function of the system address for SDRAM devices.
The mapping of the system address into memory row and column addresses is influenced
by the column address configuration provided for each bank.
■
On page misses, a row address followed by a column address is generated during an
SDRAM access.
■
On page hits, only a column address is generated during an SDRAM access.
Table 10-7 shows the ÉlanSC520 microcontroller address mapping.
.
Notes: PC refers to SDRAM precharge signaling. BA1–BA0 are the SDRAM Bank Address signals.
Table 10-7
Address Mapping to MAx Signals for SDRAM Devices
SDRAM (16 Mbit–256 Mbit)
SDRAM Configuration
Bank
Selection
MAx Pin Mapping
Column Address
Width
BA1
BA0
12
11
10
9
8
7
6
5
4
3
2
1
0
8
2-bank
Row
24
10
23
22
13
12
11
21
20
19
18
17
16
15
14
Column
24
10
PC
11
10
9
8
7
6
5
4
3
2
4-bank
Row
22
10
24
23
13
12
11
21
20
19
18
17
16
15
14
Column
22
10
PC
11
10
9
8
7
6
5
4
3
2
9
2-bank
Row
25
11
24
23
13
12
22
21
20
19
18
17
16
15
14
Column
25
11
PC
11
10
9
8
7
6
5
4
3
2
4-bank
Row
23
11
25
24
13
12
22
21
20
19
18
17
16
15
14
Column
23
11
PC
11
10
9
8
7
6
5
4
3
2
10
2-bank
Row
26
12
25
24
13
23
22
21
20
19
18
17
16
15
14
Column
26
12
PC
11
10
9
8
7
6
5
4
3
2
4-bank
Row
24
12
26
25
13
23
22
21
20
19
18
17
16
15
14
Column
24
12
PC
11
10
9
8
7
6
5
4
3
2
11
2-bank
Row
27
13
26
25
24
23
22
21
20
19
18
17
16
15
14
Column
27
13
12
PC
11
10
9
8
7
6
5
4
3
2
4-bank
Row
25
13
27
26
24
23
22
21
20
19
18
17
16
15
14
Column
25
13
12
PC
11
10
9
8
7
6
5
4
3
2
Содержание Elan SC520
Страница 1: ...lan SC520 Microcontroller User s Manual Order 22004A...
Страница 4: ...iv lan SC520 Microcontroller User s Manual...
Страница 28: ...Introduction xxviii lan SC520 Microcontroller User s Manual...
Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...