I'm bit-banging for the SPI. No problem here: I can successfully configure the MAX3140, read/write to all registers and I recieve the correct data from all registers. This tells me the Bit-Bang SPI code is working? Here's a snap shot.

;**************************************************************************
;  Read/Write 16-bit Register MAX3140
;      
;**************************************************************************

WRITE_MAX3140_16BIT_REGISTER:
			
			CLR     CS_3140 
			MOV     A,MAX3140_WRITE_REGISTER   ;Get HB
			  
			MOV     R2,#8
			SETB    DIN_3140   ;make sure DIN is input

HBYTE_3140:             RLC     A
			MOV     DIN_3140,C	           ;Write
			SETB    SCLK_3140
			MOV     C,DOUT_3140                ;Read	
			CLR     SCLK_3140
			MOV     ACC.0,C
			DJNZ    R2,HBYTE_3140
			MOV     MAX3140_READ_REGISTER,A 
			;
 			;Get LByte
			;
			MOV     A,MAX3140_WRITE_REGISTER+1 
			MOV     R2,#8
			SETB    DIN_3140                   
LBYTE_3140:             RLC     A
			MOV     DIN_3140,C	 
			SETB    SCLK_3140
			MOV     C,DOUT_3140  
			CLR     SCLK_3140
			MOV     ACC.0,C
			DJNZ    R2,LBYTE_3140
			MOV     MAX3140_READ_REGISTER+1,A 
			SETB    CS_3140
			RET


 

However, the more I dig into this, the more frustrated I get.

As it turns out, if I "Delay" after sending each Character 'Tx' it works fine. However, I don't understand why if I read the cause of the IRQ from MAX3140 and Clear my TM (Transmit Registers) before writing a new character -why this does not work.

I hate just putting in a "Dummy Delay" after each Character. Here's what I have. Again, this works! But it's not elegant and not quite right.

I'm sure I am over-looking something in the data sheet or I have an error in my code.

CMD9:  		;WRITE DATA Register to send Tx	Character
		;
		MOV   MAX3140_WRITE_REGISTER,#80H  ;TE=0; RTS HIGH For Output
		MOV   MAX3140_WRITE_REGISTER+1,#02H    ;Data to Tx 'STX'
		LCALL WRITE_MAX3140_16BIT_REGISTER
		;			
       		JNB   IRQ_3140, IRQ_1
IRQ_1:          MOV   R1,#200
LOOP1:          NOP
		NOP
		DJNZ  R1,LOOP1
    		;