Figure 15-70 and Figure 15-71 show a synchronous single-read operation with GPMCFCLKDIVIDER equal to 0 and 1, respectively.
For formulas to calculate timing parameters, see Section 15.4.5.6.1, GPMC Timing Parameters Formulas.
Table 15-456 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 15.4.4.8.2.3, Address/Data-Multiplexing Interface.
- Chip-select signal nCS:
- nCS assertion time is controlled by the GPMC_CONFIG2_i[3:0] CSONTIME bit field and ensures address setup time to nCS assertion.
- nCS deassertion time is controlled by the GPMC_CONFIG2_i[12:8] CSRDOFFTIME bit field and ensures address hold time to 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.
- Initial latency for the first read data is controlled by GPMC_CONFIG5_i[20:16] RDACCESSTIME bit field or by monitoring the WAIT signal.
- Total access time (the GPMC_CONFIG5_i[4:0] RDCYCLETIME bit field) corresponds to RDACCESSTIME plus the address hold time from nCS deassertion, plus time from RDACCESSTIME to CSRDOFFTIME.
- Direction signal DIR: DIR goes from OUT to IN at the same time as nOE assertion.
When the GPMC generates a write access to an AAD-multiplexed device, all address bits are driven onto the address/data bus in two separate phases. The first phase is used for the MSB address and is qualified with nOE driven low. The second phase for LSB address is qualified with nOE driven high. The address phase ends at nWE assertion time.
The nCS and DIR signals are controlled in the same way as for a synchronous single-read operation on an address/data-multiplexed device.
- Address valid signal nADV is asserted and deasserted twice during a read transaction:
- nADV first assertion time is controlled by the GPMC_CONFIG3_i[6:4] ADVAADMUXONTIME bit field.
- nADV first deassertion time is controlled by the GPMC_CONFIG3_i[26:24] ADVAADMUXRDOFFTIME bit field.
- nADV second assertion time is controlled by the GPMC_CONFIG3_i[3:0] ADVONTIME bit field.
- nADV second deassertion time is controlled by the GPMC_CONFIG3_i[12:8] ADVRDOFFTIME bit field.
- Output Enable signal nOE is asserted and deasserted twice during a read transaction (nOE second assertion indicates a read cycle):
- nOE first assertion time is controlled by the GPMC_CONFIG4_i[6:4] OEAADMUXONTIME bit field.
- nOE first deassertion time is controlled by the GPMC_CONFIG3_i[15:13] OEAADMUXOFFTIME bit field.
- nOE second assertion time is controlled by the GPMC_CONFIG4_i[3:0] OEONTIME bit field.
- nOE second deassertion time is controlled by the GPMC_CONFIG4_i[12:8] OEOFFTIME bit field.
After a read operation, if no other access (read or write) is pending, the data bus is driven with the previous read value. See Section 15.4.4.9.10, Bus Keeping Support.