mcf5307cft90b Freescale Semiconductor, Inc, mcf5307cft90b Datasheet - Page 254

• Manufacturer Part Number: mcf5307cft90b
• Description: Mcf5307 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

Synchronous Operation
11.4.3.2 DRAM Address and Control Registers (DACR0/DACR1) in
The DRAM address and control registers (DACR0 and DACR1), shown in Figure 11-16,
contain the base address compare value and the control bits for both memory blocks 0 and
1 of the DRAM controller. Address and timing are also controlled by bits in DACRn.
11-20
10–9
Reset
Bits
8–0
Field
Addr
12
11
R/W
31
Name
Table 11-12. DCR Field Descriptions (Synchronous Mode) (Continued)
RTIM
COC
RC
IS
Figure 11-16. DACR0 and DACR1 Registers (Synchronous Mode)
Synchronous Mode
Command on SDRAM clock enable (SCKE). Implementations that use external multiplexing
(NAM = 1) must support command information to be multiplexed onto the SDRAM address bus.
0 SCKE functions as a clock enable; self-refresh is initiated by the DRAM controller through DCR[IS].
1 SCKE drives command information. Because SCKE is not a clock enable, self-refresh cannot be
Initiate self-refresh command.
0 Take no action or issue a
1 If DCR[COC] = 0, the DRAM controller sends a
Refresh timing. Determines the timing operation of auto-refresh in the DRAM controller. Specifically,
it determines the number of clocks inserted between a
command. This same timing is used for both memory blocks controlled by the DRAM controller. This
corresponds to t
00 3 clocks
01 6 clocks
1x 9 clocks
Refresh count. Controls refresh frequency. The number of bus clocks between refresh cycles is
(RC + 1) * 16. Refresh can range from 16–8192 bus clocks to accommodate both standard and
low-power DRAMs with bus clock operation from less than 2 MHz to greater than 50 MHz.
The following example calculates RC for an auto-refresh period for 4096 rows to receive 64 mS of
refresh every 15.625 µs for each row (625 bus clocks at 40 MHz). This operation is the same as in
asynchronous mode.
# of bus clocks = 625 = (RC field + 1) * 16
RC = (625 bus clocks/16) -1 = 38.06, which rounds to 38; therefore, RC = 0x26.
used (setting DCR[IS]). Thus, external logic must be used if this functionality is desired. External
multiplexing is also responsible for putting the command information on the proper address bit.
in low-power, self-refresh state where they remain until IS is cleared, at which point the controller
sends a
while the SDRAMs are in self-refresh; the SDRAM controls the refresh period.
Uninitialized
BA
SELFX
Freescale Semiconductor, Inc.
RC
For More Information On This Product,
command for the SDRAMs to exit self-refresh. The refresh counter is suspended
in the SDRAM specifications.
18
MBAR+0x108 (DACR0); 0x110(DACR1)
Go to: www.freescale.com
SELFX
MCF5307 User’s Manual
17
—
16
command to exit self refresh.
RE
15
0
Description
—
R/W
14
13
CASL —
SELF
Uninitialized
12
command to both SDRAM blocks to put them
REF
11
command and the next possible
10
CBM
9
8
— IMRS
7
0
6
5
PS
Uninitialized
4
IP PM —
3
ACTV
2
1 0