In this post (http://www.8052.com/forum/read.phtml?id=35103) Charles describes the interconnect between an 8051 and a max186.

I see the /CS - 1/0 connection (I believe it's 1/0 not I/O, correct me if I'm wrong). My understanding is that this is just 'any' line that can be set/cleared.

MOSI and MISO are pretty easy (also just 'plain' old pins)

What I don't get though is where I get SCK(SK*) from on the MCU.

I still don't exactly understand how I can get SCLK to be a 'clock'.

I have seen a little more detail about this circuit described as follows:

P1.0 < Dout - data from 186 to 8051
P1.1 > Din - data from 8051 to 186
P1.2 > SCLK - 'strobe' from 8051 to 186
P1.3 > CS - pull low to start 186 xfer

With the following .asm to move the data out and then in:

        mov     r1,#01
        call    readadc
        ....

readadc:
        clr     p1.3               ; take CS low to wake up the MAX186
        mov     a,r1               ; prepare a control byte
        rl      a                  ; channel select bits need to end up
        rl      a                  ;   in a.6 through a.4
        rl      a
        rl      a
        orl     a,#10001110b       ; complete the control byte

        mov     r0,#8              ; initialize bit counter
nbit1:  rlc     a                  ; send the control byte, MSB first
        mov     p1.1,c
        setb    p1.2               ; pulse SCLK between bits
        clr     p1.2
        djnz    r0,nbit1           ; repeat for all eight control bits

This will probably too be a stupid question, but how do the 186 and the 8051 speak at the same rate? When I send the first byte out the P1.1, how do the two pieces sync?