;=======================================================================
; WIRING ISP
;-----------------------------------------------------------------------
SCK     P3.5
MISO    P3.4
MOSI    P3.3
RESET   P3.2
;-----------------------------------------------------------------------
If the target has reset pulldown, there is need to add pullup resistor
to reset pin at least twice less then pulldown on-board resistor or ~2k
;=======================================================================
;
;=======================================================================
; UPLOADER STATES
;-----------------------------------------------------------------------
READY           LED blinks with long on and short off periods
DOWNLOADING     LED is off
UPLOADING       LED is on
SUCCESS         LED blinks with equal on and off periods
ERROR           LED blinks with long off and short on periods
;=======================================================================
;
;=======================================================================
; OPERATING
;-----------------------------------------------------------------------
1.Upload s51uploader into sz89S51 board and run.
  READY state must be entered.
2.Connect controller to be programmed.
3.Upload target binary image into sz89S51 in same way as s51uploader.
  DOWNLOADING, UPLOADING & SUCCESS stages have to pass cosequentially, 
  or sadly ERROR state may occur.
4.To repeat operation restart sz89S51 board with START (P2.7) pressed.
;=======================================================================
;
;=======================================================================
; NOTES
;-----------------------------------------------------------------------
1.ERROR state may appear in these cases:
 - MCU is not connected, connected improperly, strong onboard pulldown.
 - MCU is not responding (do not enter programming mode)
 - MCU is too slow or no clocking (SCK period here is about ~100us+) 
 - There is an error appeared while afterwrite verification.
2.Only write operation with simultaneus verification is supporting. 
  No identification, no reading, no locking, no separate erasing.
3.To erase MCU only it is possible to write there just an image of one
  or more 0FFh bytes.
4.There is no image size checking: if it is too large and cross sz89S51
  on-board RAM boundary, it may overwrite s51uploader code and lead it
  to misworking. There should not be a problem with image 1k less then
  on-board RAM size.
5.AT89S51 ISP protocol is supported only. Target MCU is not checked. Any
  MCU with the similar algorythm may be programmed. 
;=======================================================================
         
  
