```
  // 8c/bit -> 6 MHz SCLK @ 48 MHz CLKOUT
#define BIT(bit) \
  mov  c, acc+bit      /*2c*/ \
  clr  _IOB+PINB_SCK   /*2c*/ \
  mov  _IOB+PINB_SI, c /*2c*/ \
  setb _IOB+PINB_SCK   /*2c*/

__asm
  // Use the 1st autopointer to automatically traverse the buffer.
  mov  _AUTOPTRSETUP, #0b11 ; APTR1INC|APTREN
  mov  _AUTOPTRL1, _DPL0
  mov  _AUTOPTRH1, _DPH0
  mov  dptr, #_XAUTODAT1