Everything looks quite normal in your code. However you omit the DISPLAY, READ and DATAWRT functions, so it is not possible to assemble your program.

Are you sure that the READ function works ok?

Everyone has different style of commenting. I am assuming that OUTDATA uses the B rightmost bits of the value in DPTR. One brief comment to document the input and output of each function would be helpful.

; send 8 bit mode Write Enable command
; n.b. 16 bit mode is EWEN + 6 don't care bits (11 total)
        MOV DPTR,#100110000000B            ;EWEN cmd + 7 dont care bits
        MOV B,#12                          ;NUMBER OF VALID BITS
        LCALL OUTDATA                      ;SHIFT OUT DATA MSB FIRST

 

There is an inconsistency with your quoted part numbers. I looked at the AT93C66A data sheet, and the device can be configured for 8 bit or 16 bit access.

David.