ACE25C400

4MB Serial Flash Memory

VER 1.2

14

Fast Read (0Bh)

The Fast Read instruction is similar to the Read Data instruction except that it can operate at the

highest possible frequency of FR (see “12.6 AC Electrical Characteristics”). This is accomplished by

adding eight “dummy” clocks after the 24-bit address as shown in Figure 10. The dummy clocks allow

the devices internal circuits additional time for setting up the initial address. During the dummy clocks

the data value on the DO pin is a “don’t care”.

Figure 10 Fast read instruction

Fast Read Dual Output (3Bh)

The Fast Read Dual Output (3Bh) instruction is similar to the standard Fast Read (0Bh) instruction

ACE25C400 at twice the rate of standard SPI devices. The Fast Read Dual Output instru ction is ideal

for quickly downloading code from Flash to RAM upon power-up or for applications that cache

code-segments to RAM for execution.

Similar to the Fast Read instruction, the Fast Read Dual Output instruction can operate at the

highest possible

frequency of FR (see “12.6 AC Electrical Characteristics”). This is accomplished by

adding eight “dummy” clocks after the 24-bit address as shown in Figure 11. The dummy clocks allow

the device's internal circuits additional time for setting up the initia l address. The input data during the

dummy clocks is “don’t care”. However, the DQ

edge of the first data out clock.