Chapter 9. SDRAM Controller
9-7
SDRAM Registers
of an activated page. Each bank can have one open page. A device with two banks can have
two open pages. A device with four banks can have four open pages.
The lower addresses of the row address are compared against the page address register
content. If it does not match, the SDRAM controller precharges the open page on the
accessed bank and activates the new required page. After this, the SDRAM controller
executes the
READ
or
WRITE
command. Concurrently, the page address register of the bank
is updated. This is called a page miss.
After a bank is activated, it remains activated until the next page access causing a page miss.
A precharge of a deactivated bank is allowed and simply ignored by the SDRAM.
If a memory access is to an open page only the
READ
or
WRITE
command is issued to the
SDRAM. This is called a page hit.
In two-page SDRAMs, banks 2 and 3 are invalid and must not be addressed. To avoid
address aliasing, the user should restrict the chip select address range to the space available
in the SDRAMs.
9.5 SDRAM Registers
The SDRAM configuration register (SDCR) and the SDRAM timing register (SDTR) are
described in the following sections. Note that SDRAM provides a mode register that is not
part of the SDRAM controller memory model. The SDRAM mode register is automatically
configured during initialization.
9.5.1 SDRAM Configuration Register (SDCR)
SDCR is used to configure the SDRAM controller address multiplexers for the type of
SDRAM devices used on the system board.
Table 9-7 describes SDCR fields.
15
14
13
12
11
10
8
7
6
5
4
3
2
1
0
Write
—
MCAS
—
BALOC
GSL
—
REG INV SLEEP ACT INIT
Reset
0
00
00
001
0
00
0
1
0
0
0
R/W
Read/Write
Read-only
R/W
Addr
MBAR + 0x0180
Figure 9-3. SDRAM Configuration Register (SDCR)
Summary of Contents for DigitalDNA ColdFire MCF5272
Page 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Page 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Page 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Page 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Page 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Page 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Page 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Page 338: ...13 44 MCF5272 User s Manual Application Examples ...
Page 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Page 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Page 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Page 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...