AX88180 datasheet(44/47 Pages) ASIX

44 / 47 page

AX88180

ASIX ELECTRONICS CORPORATION

Appendix A4. Synchronous and asynchronous timing selection

AX88180 can support synchronous or asynchronous access from host MCU. Below information provides some

references to select clock frequency of host MCU and AX88180.

A4-1. AX88180 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

A4-2. AX88180 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 AX88180 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 AX88180.

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 AX88180.

AX88180 Datasheet(PDF) 44 Page - ASIX Electronics Corporation