GD25Q21 datasheet(39/49 Pages) ELM

39 / 49 page

Rev.1.1

49 -

http://www.elm-tech.com

GD25Q21BxIGx Uniform Sector Dual and Quad Serial Flash

7.31. Continuous Read Mode Reset (CRMR) (FFH)

The Dual/Quad I/O Fast Read operations, “Continuous Read Mode” bits (M7-0) are implemented to further

reduce command overhead. By setting the (M7-0) to AXH, the next Dual/Quad I/O Fast Read operations do not

require the BBH/EBH/E7H command code.

If the system controller is reset during operation it will likely send a standard SPI command, such as Read ID

(9FH) or Fast Read (0BH), to the device. Because the GD25Q21B has no hardware reset pin, so if Continuous

Read Mode bits are set to “AXH”, the GD25Q21B will not recognize any standard SPI commands. So

Continuous Read Mode Reset command will release the Continuous Read Mode from the “AXH” state and

allow standard SPI command to be recognized. The command sequence is show below.

Figure 36. Continuous Read Mode Reset Sequence Diagram

0 1 2 3 4 5 6 7

CS#

SCLK

SI(IO0)

SO(IO1)

WP#(IO2)

HOLD#(IO3)

FFH

Mode Bit Reset for Quad/Dual I/O

Don`t Care

7.32. Program/Erase Suspend (PES) (75H)

The Erase/Program Suspend instruction “75H”, allows the system to interrupt a sector/block erase or page

program operation and then read data from any other sector or block. The Write Status Register command (01H),

Page Program command (02H) and Erase commands (20H, 52H, D8H, C7H, 60H) are not allowed during

suspend. Erase/Program Suspend is valid only during the sector/block erase or page program operation. A

maximum of time of “tsus” (See AC Characteristics) is required to suspend the program/erase operation.

While the Erase/Program suspend cycle is in progress, the Read Status Register command may still be

accessed for checking the status of the BUSY bit. The BUSY bit is a 1 during the Erase/Program suspend cycle

and becomes a 0 when the cycle is finished and the device is ready to accept read command. A power-off during

the suspend period will reset the device and release the suspend state. The command sequence is show below.

Figure 37. Program/Erase Suspend Sequence Diagram

Command

0 1 2 3 4 5 6 7

75H

CS#

SCLK

High-Z

tSUS

Accept read command

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