AX88780 datasheet(52/55 Pages) ASIX

52 / 55 page

AX88780

ASIX ELECTRONICS CORPORATION

Appendix A3. Synchronous and asynchronous timing selection

AX88780 can support synchronous or asynchronous access from host MCU. Below information provides some

references to select clock frequency of host MCU and AX88780.

A3-1. AX88780 is synchronous with host MCU.

The timing selection is suitable for both 32-bit and 16-bit mode.

Frequency

Access type

Valid access timing (OEN/WEN active timing)

Max 100MHz

Single or Burst

Min 5 clocks

A3-2. AX88780 is asynchronous to host MCU.

The timing selection is suitable for both 32-bit and 16-bit mode.

Frequency

Access type

Valid access timing (OEN/WEN active timing)

Max 100MHz

Single or Burst

Min 6 reference clocks (Note)

Note: The reference clock is from OSC, and it’s not the output of host MCU. For instance, if AX88780 runs in

asynchronous mode and refers a 100MHz clock from OSC, whereas MCU runs in 125Mhz environment. In

such condition, MCU must at least offer 60ns (min 6 reference clock of 100Mhz) access timing to AX88780.

The 60ns for MCU is almost reached to 8 clocks (125MHz). We recommend that it is needed to extend the

access timing of MCU to AX88780.

AX88780 Datasheet(PDF) 52 Page - ASIX Electronics Corporation