GPMC
Any access attempted to a nonvalid GPMC address region (CSVALID disabled or address decoding
outside a valid chip-select region) is not propagated to the external interface and a GPMC access error is
posted. In case of chip-selects overlapping, an error is generated and no access will occur on either chip-
select. Chip-select 0 is the only chip-select region enabled after either a power-up or a GPMC reset.
Although the GPMC interface can drive up to seven chip-selects, the frequency specified for this interface
is for a specific load. If this load is exceeded, the maximum frequency cannot be reached. One solution is
to implement a board with buffers, to allow the slowest device to maintain the total load on the lines.
7.1.3.3.8.2 Access Protocol
7.1.3.3.8.2.1 Supported Devices
The access protocol of each chip-select can be independently specified through the
GPMC_CONFIG1_i[11-10] DEVICETYPE parameter for:
•
Random-access synchronous or asynchronous memory like NOR flash, SRAM
•
NAND flash asynchronous devices
For more information about the NAND flash GPMC basic programming model and NAND support, see
and
7.1.3.3.8.2.2 Access Size Adaptation and Device Width
Each chip-select can be independently configured through the GPMC_CONFIG1_i[13-12] DEVICESIZE
field to interface with a 16-bit wide device or an 8-bit wide device. System requests with data width greater
than the external device data bus width are split into successive accesses according to both the external
device data-bus width and little-endian data organization.
An 8-bit wide device must be interfaced to the D0-D7 external interface bus lane. GPMC data accesses
only use this bus lane when the associated chip-select is attached to an 8-bit wide device.
The 8-bit wide device can be interfaced in asynchronous or synchronous mode in single data phase (no 8-
bit wide device burst mode). If the 8-bit wide device is set in the chip-select configuration register,
ReadMultiple and WriteMultiple bit fields are considered “don’t care” and only single accesses are
performed.
A 16-bit wide device can be interfaced in asynchronous or synchronous mode, with single or multiple data
phases for an access, and with native or emulated wrap mode support.
7.1.3.3.8.2.3 Address/Data-Multiplexing Interface
For random synchronous or asynchronous memory interfacing (DEVICETYPE = 0b00), an address- and
data-multiplexing protocol can be selected through the GPMC_CONFIG1_i[[9-8] MUXADDDATA bit field.
The ADVn signal must be used as the external device address latch control signal. For the associated
chip-select configuration, ADVn assertion and deassertion time and OEn assertion time must be set to the
appropriate value to meet the address latch setup/hold time requirements of the external device (see
This address/data-multiplexing interface is not applicable to NAND device interfacing. NAND devices
require a specific address, command, and data multiplexing protocol (see
7.1.3.3.8.3 External Signals
7.1.3.3.8.3.1 WAIT Pin Monitoring Control
GPMC access time can be dynamically controlled using an external gpmc_wait pin when the external
device access time is not deterministic and cannot be defined and controlled only using the GPMC internal
RDACCESSTIME, WRACCESSTIME and PAGEBURSTACCESSTIME wait state generator.
The GPMC features two input wait pin:gpmc_wait1, and gpmc_wait0. This pin allow control of external
devices with different wait-pin polarity. They also allow the overlap of wait-pin assertion from different
devices without affecting access to devices for which the wait pin is not asserted.
265
SPRUH73H – October 2011 – Revised April 2013
Memory Subsystem
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