Register Descriptions
1231
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
External Peripheral Interface (EPI)
17.11.4 EPI SDRAM Configuration (EPISDRAMCFG) Register, offset 0x010
NOTE:
The MODE field in the EPICFG register determines which configuration register is accessed
for offsets 0x010 and 0x014.
To access EPISDRAMCFG, the MODE field must be 0x1.
The SDRAM Configuration register is used to specify several parameters for the SDRAM controller. Note
that this register is reset when the MODE field in the EPICFG register is changed. If another mode is
selected and the SDRAM mode is selected again, the values must be reinitialized..
The SDRAM interface designed to interface to x16 SDRS DRAMs of 64 MHz or higher, with the address
and data pins overlapped (wire ORed on the board). See
for pin assignments.
Figure 17-31. EPI SDRAM Configuration (EPISDRAMCFG) Register [offset 0x010]
31
30
29
27
26
16
FREQ
Reserved
RFSH
R/W-0x1
R-0x0
R/W-0x2EE
15
10
9
8
2
1
0
Reserved
SLEEP
Reserved
SIZE
R-0
R/W-0
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 17-17. EPI SDRAM Configuration (EPISDRAMCFG) Register Field Descriptions
Bit
Field
Value
Description
31-30
FREQ
Frequency Range
This field configures the frequency range used for delay references by internal counters. This EPI
frequency is the system frequency with the divider programmed by the COUNT0 bit in the
EPIBAUDn register bit. This field affects the power up, precharge, and auto refresh delays. This
field does not affect the refresh counting, which is configured separately using the RFSH field (and
is based on system clock rate and number of rows per bank). The ranges are:
0x0
0 - 15 MHz
0x1
15 - 30 MHz
0x2
30 - 50 MHz
0x3
50 - 100 MHz
29-27
Reserved
Reserved
26-16
RFSH
Refresh Counter
This field contains the refresh counter in system clocks. The reset value of 0x2EE provides a
refresh period of 64 ms when using a 50 MHz clock.
15-10
Reserved
Reserved
9
SLEEP
Sleep Mode
0
No effect
1
The SDRAM is put into low power state, but is self-refreshed.
8-2
Reserved
Reserved
1-0
SIZE
Size of SDRAM
The value of this field affects address pins and behavior.
0x0
64 megabits (8MB)
0x1
128 megabits (16MB)
0x2
256 megabits (32MB)
0x3
512 megabits (64MB)