Cypress FM4 Series - External RDY

CHAPTER 14: External Bus Interface
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 781
3.8 External RDY
The following explains the external RDY function.
This function allows extended access cycle inserting wait cycles while L level is input to the MRDY pin.
This enables accesses to the low speed external memories. The operation waveform of the RDY signal is
shown in Figure 3-18.
Figure 3-18 Operation of External RDY
0 1 2 3 4 5 6 7
MRDY
MOEX, MWEX
Original input
3 or more cycles
3cycle
2cycle
8 9
MOEX, MWEX
Extended by MRDY
2 or more cycles
Notes:
− When you use the external RDY function, set the widths for MOEX and MWEX to 3 or more
cycles.
− In order to enable RDY function, MRDY=L must be input 2 cycles before MOEX↑/MWEX↑. The
MRDY=L less than 2 cycles will be ignored.
See External Ready Input Timing in Data Sheet of the product to be used.
− MOEX↑/MWEX↑ will be performed 2 cycles after MRDY=H.
− Do not set MRDY=L until MOEX↑/MWEX↑ when MRDY=H is set once.
− The external RDY function will not be available in NOR Flash memory page read and NAND
Flash memory modes.
− The periods of ALC and ALE will not be extended even if MRDY=L is set.
− Automatic Wait and External RDY is both possible setting.
MCLK
(MCLKOUT)