SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The GPMC_CONFIG4_i[19-16] WEONTIME bit field (where i = 0 to 3) defines the nWE signal-assertion time relative to start access time. The GPMC_CONFIG4_i[28-24] WEOFFTIME bit field defines the nWE signal-deassertion time relative to start access time. These bit fields apply only to write accesses. nWE is not asserted during a read cycle.
WEONTIME can be used to control an address and byte-enable valid setup time control before nWE assertion. WEOFFTIME can be used to control an address and byte-enable valid hold time control after nWE assertion.
nWE signal transitions as controlled through WEONTIME, and WEOFFTIME can be delayed by a half-GPMC_FCLK period by enabling the GPMC_CONFIG4_i[23] WEEXTRADELAY bit. This half-GPMC_FCLK period provides more granularity on nWE assertion and deassertion time to ensure proper setup and hold time relative to GPMC output clock. If enabled, WEEXTRADELAY applies to all parameters controlling nWE transitions.
The WEEXTRADELAY bit must be used carefully to avoid control-signal overlap between successive accesses to different chip-selects. This implies the need to program the WRCYCLETIME bit field to be greater than the nWE signal-deassertion time, including the extra half-GPMC_FCLK-period delay.