Am29F400AT

The autoselect mode allows the reading of a binarycode from the device and will identify its manufacturer and type. This mode is intended for use by programming equipment for the purpose of automatically matching the device to be programmed with its corresponding programming algorithm. This mode is functional over the entire temperature range of the device.

To activate this mode, the programming equipment must force VID (11.5 V to 12.5 V) on address pin A9.Two identifier bytes may then be sequenced from the device outputs by toggling address A0 from VIL to VIH.All addresses are don't cares except A0, A1, and A6(see Table 3).

The manufacturer and device codes may also be read via the command register, for instances when theAm29F400A is erased or programmed in a systemwithout access to high voltage on the A9 pin. The command sequence is illustrated in Table 4 (see Autoselect Command Sequence).

Byte 0 (A0 = VIL) represents the manufacturer's code  (AMD=01H) and byte 1 (A0 = VIH) the device identifier code (Am29F400AT = 23H and Am29F400AB = ABH for x8 momode;Am29F400AT = 2223H and Am29F400AB= 22ABH for x16 mode). These two bytes/words are given in the table below. All identifiers for manufacturer and device will exhibit odd parity with DQ7 defined as the parity bit. In order to read the proper device codes when executing the Autoselect, A1 must be VIL(see Tables 3 and 4).
The autoselect mode also facilitates the determination of sector protection in the system. By performing a read operation at the address location XX02H with the higher order address bits A12A17 set to the desired sector address, the device will return 01H for a protected sector and 00H for a non-protected sector.