7.6.2 High-Speed Mode

The device can be set to High-Speed mode or checked to see whether or not it is in High-Speed mode with the use of the Eh opcode. This transaction only requires eight bits. The power-on default for the AT21CS01/AT21CS11 is High-Speed mode.

To set the device to High-Speed mode, the host must send a Start condition, followed by the device address byte with the opcode of 1110b (Eh) 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 high-speed operation.

To determine if the device is already set to High-Speed mode, the device address byte with the opcode of 1110b (Eh) specified 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 High-Speed mode. It will return a NACK (logic ‘1’) if the device is not currently set for High-Speed mode.