6 Available Opcodes
Table 6-1 outlines available opcodes for the AT21CS01/AT21CS11.
| Command | 4-Bit Opcode | Brief Description of Functionality |
|---|---|---|
| EEPROM Access | 1010 (Ah) | Read/Write the contents of the main memory array. |
| Security Register Access | 1011 (Bh) | Read/Write the contents of the Security register. |
| Lock Security Register | 0010 (2h) | Permanently lock the contents of the Security register. |
| ROM Zone Register Access | 0111 (7h) | Inhibit further modification to a zone of the EEPROM array. |
| Freeze ROM Zone State | 0001 (1h) | Permanently lock the current state of the ROM Zone registers. |
| Manufacturer ID Read | 1100 (Ch) | Query manufacturer and density of device. |
| Standard Speed Mode | 1101 (Dh) | Switch to Standard Speed mode operation (AT21CS01 only command, the AT21CS11 will NACK this command). |
| High-Speed Mode | 1110 (Eh) | Switch to High-Speed mode operation (AT21CS01 power‑on default; AT21CS11 will ACK this command). |