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Example Configuration
876
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
External Memory Interface A (EMIFA)
19.3 Example Configuration
This section presents an example of interfacing the EMIFA to both an SDR SDRAM device and an
asynchronous flash device.
19.3.1 Hardware Interface
shows the hardware interface between the EMIFA, a Samsung K4S641632H-TC(L)70 64Mb
SDRAM device, and two SHARP LH28F800BJE-PTTL90 8Mb Flash memory. The connection between
the EMIFA and the SDRAM is straightforward, but the connection between the EMIFA and the flash
deserves a detailed look.
The address inputs for the flash are provided by three sources. The A[12:0] address inputs are provided
by a combination of the EMA_A and EMA_BA pins according to
. The upper address
inputs A[18:13] are provided by GPIO pins. The six GPIO pins are connected to the upper address bits of
the flash memory and attached to pulldown resistors so that their value is 0 after reset and before
configuring the pins as GPIO. This is necessary if the ROM bootloader is copying the secondary
bootloader from the flash. More details on using GPIO pins as upper address pins can be found in
. RD/BY signal from one flash is connected to EMA_WAIT pin of EMIFA. A GPIO pin can
be made use of to receive the RD/BY signal coming from the second flash, as shown in
Finally, this example configuration connects the EMA_WE pin to the WE input of the flash and operates
the EMIFA in Normal Mode.
19.3.2 Software Configuration
The following sections describe how to interface the EMIFA to SDRAM, Asynchronous SRAM (ASRAM),
or a NAND Flash device.
19.3.2.1 Configuring the SDRAM Interface
This section describes how to configure the EMIFA to interface with the Samsung K4S641632H-TC(L)70
SDRAM with a clock frequency of f
EMA_CLK
= 100 MHz. Procedure A described in
is
followed which assumes that the SDRAM power-up timing constraint were met during the SDRAM Auto-
Initialization sequence after Reset.
19.3.2.1.1 PLL Programming for the EMIFA to K4S641632H-TC(L)70 Interface
The device PLL Controller should first be programmed to select the desired EMA_CLK frequency. Before
doing this, the SDRAM should be placed in Self-Refresh Mode by setting the SR bit in the SDRAM
configuration register (SDCR). The SR bit should be set using a byte-write to the upper byte of the SDCR
to avoid triggering the SDRAM Initialization Sequence. The EMA_CLK frequency can now be adjusted to
the desired value by programming the appropriate SYSCLK domain of the PLL Controller. Once the PLL
has been reprogrammed, remove the SDRAM from Self-Refresh by clearing the SR bit in SDCR, again
with a byte-write.
Table 19-26. SR Field Value For the EMIFA to K4S641632H-TC(L)70 Interface
Field
Value
Purpose
SR
1 then 0
To place the EMIFA into the self refresh state