7.6.1 Standard Speed Mode (AT21CS01 only)

The AT21CS01 can be set to Standard Speed mode or checked to see whether or not it is in Standard Speed mode with the use of the Dh opcode. This transaction only requires eight bits.

To set the device to Standard Speed mode, the host must send a Start condition, followed by the device address byte with the opcode of 1101b (Dh) specified, along with the appropriate client address combination and the Read/Write bit set to a logic ‘0’. The device will return an ACK (logic ‘0’) and will be immediately ready to receive commands for standard speed operation.

To determine if the device is already set to Standard Speed mode, the device address byte with the opcode of 1101b (Dh) must be sent to the device, along with the appropriate client address combination and the Read/Write bit set to a logic ‘1’. The device will return an ACK (logic ‘0’) if it is set for Standard Speed mode. It will return a NACK (logic ‘1’) if the device is not currently set for Standard Speed mode.