LE25S40AMC

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2. Dual read

There are two Dual read commands, the Dual Output read command and the Dual I/O read command. They achieve the

twice speed-up from a High-speed read command.

2-1. Dual Output read command

The Dual Output read command changes SI/SIO0 into the output pin function in addition to SO/SIO1, makes the data

output x2 bit and has achieved a high-speed output. Consisting of the first through fifth bus cycles, the Dual Output read

command inputs the 24-bit addresses and 8 dummy bits following (3Bh). DATA1 (Bit7, BIt5, Bit3 and Bit1) is output

from SI/SIO0 and DATA0 (Bit6, Bit4, Bit2 and Bit0) is output from SO/SIO1 on the falling clock edge of fifth bus

cycle bit 0 as a reference. "Figure 5-a Dual Output read" shows the timing waveforms.

Figure 5-a. Dual Output read

2-2. Dual I/O read command

The Dual I/O read command changes SI/SIO0 and SO/SIO1 into the input output pin function, makes the data input and

output x2 bit and has achieved a high-speed output. Consisting of the first through third bus cycles, the Dual I/O read

command inputs the 24-bit addresses and 4 dummy clocks following (BBh). The format of the address input and the

dummy bit input is the x2 bit input. Add1 (A23, A21, -, A3 and A1) is input from S0/SIO1 and Add0 (A22, A20, -, A2

and A0) is input from SI/SIO0. 2CLK of the latter half of the dummy clock is in the state of high impedance, the

controller can switch I/O for this period. DATA1 (Bit7, BIt5, Bit3 and Bit1) is output from SI/SIO0 and DATA0 (Bit6,

Bit4, Bit2 and Bit0) is output from SO/SIO1 on the falling clock edge of third bus cycle bit 0 as a reference. "Figure 5-b

Dual I/O Read" shows the timing waveforms.

Figure 5-b. Dual I/O Read

When SCK is input continuously after the read command has been input and the data in the designated addresses has

been output, the address is automatically incremented inside the device while SCK is being input, and the

corresponding data is output in sequence. If the SCK input is continued after the internal address arrives at the highest

address (7FFFFh), the internal address returns to the lowest address (00000h), and data output is continued. By setting

the logic level of CS to high, the device is deselected, and the read cycle ends. While the device is deselected, the output

pin SO is in a high-impedance state.

CS

High Impedance

DATA1

DATA1

DATA1

SCK

SO/SIO1

SI/SIO0

3Bh

Add.

Add.

Add.

15

MSB

MSB

0

1

2

3

4

5

6

7

8

23

16

24

31 32

39 40

43 44

47

Mode3

Mode0

8CLK

MSB

MSB

N+2

N+1

N

DATA0

DATA0

DATA0

4CLK

4CLK

DATA0

b6,b4,b2,b0

DATA1

b7,b5,b3,b1

dummy

bit

CS

High Impedance

DATA1

DATA1

DATA1

SCK

SO/SIO1

SI/SIO0

BBh

X

Add1:A22,A20-A2,A0

MSB

MSB

0

1

2

3

4

5

6

7

8

19

22 23 24

27 28

31

Mode3

Mode0

8CLK

MSB

MSB

N+2

N+1

N

DATA0

DATA0

DATA0

4CLK

DATA0

b6,b4,b2,b0

DATA1

b7,b5,b3,b1

dummy

bit

20 21

Add2:A23,A21-A3,A1

X

2CLK

2CLK

12CLK