Schematic of a very simple RS232-Interface for the TK-230/330

                                 munralamun@yahoo.com
  
  
    userport                       MAX232         rs232   9pin  25pin
                                +----------+
                                !          !
                                !          !
              !                 !    /!    !
not used    --*--------------------O< !---------  rxd     2      3
              !                9!    \!    !8
                                !          !
                                !          !
                                !          !
              !                 !          !
                                !          !
                                !  !\      !
not used    --*--------------------! >O---------  txd     3      2
              !               11!  !/      !14
                                !          !
                                !          !
                                !          !
                                !  !\      !
Pin 5 on radio------>--------------! >O---------  rts     7      4
                              10!  !/      !7
                                !          !
                                !    /!    !
Pin 6 on radio-------<-----*-------O< !---------  cts     8      5
                              12!    \!    !13
                                !          !
                                !          !---   gnd     5      7
                                !          !15
                                !          !      
                                !          !
                                !          !      
                                !          !
                                !          !      
                    c2  ! !+    !          !
         +5v------------! !-----!          !      
                        ! !    2!          !
                                !          !
                    c4 +! !     !          !
         gnd------------! !-----!          !
                        ! !    6!          !
                                !          !
                     c1 ! !+    !          !
                      +-! !-----!          !
                      ! ! !    1!          !
                      !         !          !
                      +---------!          !
                               3!          !
                     c3 ! !+    !          !
                      +-! !-----!          !
                      ! ! !    4!          !
                      !         !          !
                      +---------!          !
                               5!          !
                                !          !
         gnd--------------------!          !
                              15!          !
                                !          !
         +5V--------------------!          !
                              16+----------+

  

| remark: The MAX232 needs 4 capacitors to generate +/- 10 volts to
|         drive the RS-232 unit.  The values are as such:  (in uF)

|         IC       C1   C2   C3   C4                        
|         -------  ---  ---  ---  ---
|         MAX232   1.0  1.0  1.0  1.0  
|         MAX232A  0.1  0.1  0.1  0.1  
|         MAX232E  1.0  1.0  1.0  1.0  
                         
  notes :
     


     Top view of the used ICs:
  
                                      MAX232
                                     +------+
                              +cap1 -!1 \/16!- Vcc (to 5v reg)
                              +cap2 -!      !- GND (power neg)
                              -cap1 -!      !- RS232/txd [not used]
                              +cap3 -!      !- RS232/cts
                              -cap3 -!      !- TTL/^cts
                              -cap4 -!      !- TTL/txd [not used]
                          RS232/rts -!      !- TTL/^rts
             [not used]   RS232/rxd -!8    9!- TTL/rxd [not used]
                                     +------+