SMC Networks AHB SRAM/NOR, PL241 manual 19 Synchronous burst read

Models: AHB SRAM/NOR PL241

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Figure 2-19 Synchronous burst read

Functional Overview

Figure 2-19shows a burst read with the smc_wait_0 output of the memory used to delay the transfer.

Note

Synchronous memories have a configuration register enabling smc_wait_0 to be asserted either on the same clock cycle as the delayed data or a cycle earlier. The SMC only supports smc_wait_0 being asserted one cycle early, enabling smc_wait_0 to be initially sampled with the fed back clock and then with smc_mclk0 before being used by the FSM. This enables the easiest timing closure. Additionally, you must configure the memory for smc_wait_0 to be active LOW.

In synchronous operation, the SMC relies on the smc_wait_0 signal being deasserted HIGH to indicate that the memory can finish the transfer. When in synchronous mode some memories do not deassert the smc_wait_0 signal during non-array read transfers. Non-array read transfers are typically status register reads. To avoid stalling the system with these memories, in synchronous mode you must not perform non-array read transfers with the memory and SMC.

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Figure 2-19 Synchronous burst read

ARM DDI 0389B

Copyright © 2006 ARM Limited. All rights reserved.

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Page 53
Image 53
SMC Networks AHB SRAM/NOR, PL241 manual 19 Synchronous burst read