User manual

LPCXpresso Experiment Kit - User’s Guide

Page 83

Figure 49 –25LC080 Instruction Set

To read in the memory region, a start address (16-bit address) is transmitted after the READ

instruction. In total, three bytes are transmitted from the microcontroller to the 25LC080 chip before

bytes can be read from the memory. As many bytes that are of interest can be read out in the read

operation. An internal address counter is incremented after each transmitted byte. If the highest

address is reached (0x03FF for this chip), the address counter rolls over to address 0x0000. Note that

the SSEL signal (or CS that it is called in the picture below) is low during the complete operation.

Figure 50 –25LC080 Read Sequence

To write in the memory region, the WRITE instruction is used. Similar to the read operation, a 16-bit

address is transmitted to set the start address of the write operation. One or many bytes can be written

at the same time, see the pictures below.

Figure 51 –25LC080 Byte Write Sequence

Depending on chip version (C or D, check chip package marking for details), the maximum number of

bytes to write is 16 or 32. Note that all bytes must be in the same page. Physical page boundaries start

at addresses that are integer multiples of the page buffer size (16 or 32 bytes). It is for example

allowed to write 7 bytes from address 4 to 10. It is not allowed to write 7 bytes from address 27 to 33

since a page boundary will then be crossed (true for both 16 and 32 byte page versions).