GPMC_FCLK
GPMC_CLK
WAIT
Valid Address
Valid Address
Data
CSONTIME
CSWROFFTIME
ADVONTIME
ADVWROFFTIME
WEONTIME
WRDATAONADMUXBUS
WEOFFTIME
WRCYCLETIME
nBE1/nBE0
nCS
nADV
nWE
gpmc_a[11:1]
gpmc_d[15:0]
(connected to A[26:17] on
memory side)
(connected to A[16:1] /D[15:0] on
memory side)
gpmc-013
Public Version
www.ti.com
General-Purpose Memory Controller
•
The end of the access is defined by the WRCYCLETIME parameter.
This write-cycle time is defined in the GPMC.
[12:8] WRCYCLETIME field.
After a write operation, if no other access (read or write) is pending, the data bus keeps its previous value.
See
, Bus Keeping Support.
In the GPMC, when a 16-bit wide device is attached to the controller, a Word32 write access is split into
two Word16 write accesses. For more information about GPMC access size and type adaptation, see
, System Burst Versus External Device Burst Support.
Between two successive accesses, if an nCS pulse is needed:
•
The GPMC.
[11:8] CYCLE2CYCLEDELAY field can be programmed with
GPMC.
[7] CYCLE2CYCLESAMECSEN enabled.
•
The CSWROFFTIME and CSONTIME parameters also allow a chip-select pulse, but this affects all
other types of access.
10.1.5.9.2.2 Asynchronous Single Write Operation on an Address/Data-Multiplexed Device
shows an asynchronous single write operation on an address/data-multiplexed device.
Figure 10-13. Asynchronous Single Write on an Address/Data-Multiplexed Device
When the GPMC generates a write access to an address/data-multiplexed device, it drives the address on
the address/data muxed bus until WRDATAONADMUXBUS time, and then it drives the data. For more
information, see
, Address/Data-Multiplexing Interface.
register settings (i = 0 to 7):
•
WRITEMULTIPLE bit at 0 (write single access)
•
WRITETYPE bit at 0 (write asynchronous)
•
MUXADDDATA bit at 1 (address/data-multiplexed device)
Address bits [16:1] are placed on the address/data bus at the start of cycle time, and the remaining
address bits [26:17] are placed on the address bus.
The nCS, nADV, and nWE signals are controlled in the same way as nonmultiplexed accesses.
2145
SWPU177N – December 2009 – Revised November 2010
Memory Subsystem
Copyright © 2009–2010, Texas Instruments Incorporated