AT89S4D12

The AT89S4D12 is a low-voltage, highly integrated CMOS 8-bit microcomputer with 4K bytes of downloadable Flash program memory and 128K bytes of in-system reprogrammable Flash data memory. The device is manufactured using Atmel's high density Flash memory technology and is compatible with the industry-standard MCS-51™ instruction set.

The 128K bytes of on-chip Flash data memory are accessed as two 64K byte blocks. Bit 0 at SFR location 96H is used to select the active block. The MOVX instruction is used to read and write the data memory. Both the program and data memory arrays can be programmed by an external programmer.

The downloadable Flash can be changed one page (128 bytes) at a time and is accessible through the SPI serial peripheral interface port. Holding RESET active forces the SPI bus into a slave input mode and allows the program memory to be written-from or read-to unless Lock Bit 2 has been activated.

The functional operations of the 128K bytes Flash data memory are equivalent to those on the AT29LV010A 1M Bit Flash memory device.