For formulas to calculate timing parameters, see Section 12.3.4.4.6.1, GPMC Timing Parameters Formulas.
Table 12-206 lists the timing bit fields to set up to configure the GPMC in asynchronous single-read mode.
When the GPMC generates a read access to an address/data-multiplexed device, it drives the address bus until nOE assertion time. For more information, see Section 12.3.4.3.7.2.3, Address/Data-Multiplexing Interface.
Address bits (A[16-1] from a GPMC perspective,
A[15-0] from an external device perspective) are placed on the address/data bus, and
the remaining address bits are placed on the address bus. The address phase ends at nOE
assertion, when the DIR signal goes from OUT to IN.
- Chip-select signal nCS:
- nCS assertion time is controlled by the
GPMC_CONFIG2_i[3-0] CSONTIME bit field. It controls the address setup
time to nCS assertion.
- nCS deassertion time is controlled by the
GPMC_CONFIG2_i[12-8] CSRDOFFTIME bit field. It controls the address hold
time from nCS deassertion.
- Address valid signal nADV:
- nADV assertion time is controlled by the
GPMC_CONFIG3_i[3-0] ADVONTIME bit field.
- nADV deassertion time is controlled by the
GPMC_CONFIG3_i[12-8] ADVRDOFFTIME bit field.
- Output enable signal nOE:
- nOE assertion indicates a read cycle.
- nOE assertion time is controlled by the
GPMC_CONFIG4_i[3-0] OEONTIME bit field.
- nOE deassertion time is controlled by the
GPMC_CONFIG4_i[12-8] OEOFFTIME bit field.
- Read data is latched when RDACCESSTIME completes.
Access time is defined in the GPMC_CONFIG5_i[20-16] RDACCESSTIME bit field.
- Direction signal DIR: DIR goes from OUT to IN at the same time that nOE is asserted.
- The end of the access is defined by the
GPMC_CONFIG5_i[4-0] RDCYCLETIME parameter.
In the GPMC, when a 16-bit wide device is attached to the controller, a 32-bit word write access is split into two 16-bit word write accesses. For more information about GPMC access size and type adaptation, see Section 12.3.4.3.9.5, System Burst Versus External Device Burst Support.
Between two successive accesses, if an nCS pulse is needed:
- The GPMC_CONFIG6_i[11-8] CYCLE2CYCLEDELAY bit
field can be programmed with the GPMC_CONFIG6_i[7] CYCLE2CYCLESAMECSEN bit
enabled.
- The CSWROFFTIME and CSONTIME parameters also allow a chip-select pulse, but this affects all other types of access.