8.5 Manufacturer ID Read
The AT21CS01/AT21CS11 offers the ability to query the device for manufacturer, density, and revision information. By using a specific opcode and following the format of a current address read, the device will return a 24-bit value that corresponds with the I2C identifier value reserved for Microchip, along with further data to signify a 1-Kbit density and the device revision.
To read the Manufacturer ID data, the host must send a Start condition,
followed by the device address byte with the opcode of 1100b (Ch)
specified, along with the appropriate client address combination and the
Read/Write bit set to a logic ‘1’. After the
device address byte has been sent, the AT21CS01/AT21CS11 will return an
ACK (logic ‘0’). If the Read/Write bit is set to
a logic ‘0’ to indicate a write, the device will NACK (logic
‘1’) since the Manufacturer ID data is read-only.
After the device has returned an ACK, it will send the first byte of
Manufacturer ID data, which contains the eight Most Significant bits (D23‑D16) of the
24-bit data value. The host can then return an ACK (logic ‘0’) to indicate
it successfully received the data, prompting the device to send the second byte (D15‑D8) of
Manufacturer ID data. The process repeats until all three bytes have been read out and the
host sends a NACK (logic ‘1’) to complete the sequence. Figure 8-6 depicts this sequence. If the host ACKs
(logic ‘0’) the third byte, the Internal Pointer will “roll over” to the
first byte of Manufacturer ID data.
Table 8-2 provides the format of the Manufacturer ID data.
| Device | Manufacturer Code <D23:D12> | Device Code <D11:D3> | Revision Code <D2:D0> | Hex Value <D23:D0> |
|---|---|---|---|---|
| AT21CS01 | 0000-0000-1101 | 0010-0000-0 | 000 | 00D200h |
| AT21CS11 | 0000-0000-1101 | 0011-1000-0 | 000 | 00D380h |
The Manufacturer Identifier portion of the ID is returned in the 12 Most
Significant bits of the three bytes read out. The value reserved for Microchip is
0000-0000-1101b (00Dh). Therefore, the first byte read out by the
device will be 00h. The upper nibble of the second byte read out is Dh.
The Least Significant 12 bits of the 24-bit ID is comprised of a Microchip defined value that indicates the device density and revision. Bits D11 through D3 indicate the device code and bits D2 through D0 indicate the device revision. The output is shown more specifically in Table 8-2.
The overall 24-bit value returned by the AT21CS01 is 00D200h. The overall 24‑bit value returned by the AT21CS11 is 00D380h.