...
extern "C"
{

  WSP32_API bool WINAPI AccessCOM(char *P);
  WSP32_API bool WINAPI OpenCOM(char *P, DWORD baud);
  WSP32_API bool WINAPI CloseCOM(void);
  WSP32_API bool WINAPI SetModLns(DWORD F);
  WSP32_API bool WINAPI GetModLns(LPDWORD lpD);
  WSP32_API bool WINAPI PurgeCOM(void);
  WSP32_API bool WINAPI FlushCOM(void);
  WSP32_API bool WINAPI GetMaskCOM(LPDWORD lpEvtMask);
  WSP32_API bool WINAPI SetMaskCOM(DWORD EvtMask);
  WSP32_API bool WINAPI WaitEventCOM(LPDWORD lpEvtMask);
  WSP32_API bool WINAPI RxFrame(DWORD To, unsigned char &ADD,
             unsigned char &CMD, unsigned char &N, unsigned char *Data);
  WSP32_API bool WINAPI TxFrame(unsigned char ADDR, unsigned char CMD,
             unsigned char N, unsigned char *Data);
}

interface
...
function AccessCOM(p:string):boolean;  stdcall;
function OpenCOM(p:string;baud:DWORD):boolean; stdcall;
function CloseCOM():boolean; stdcall;
function SetModLns(f:DWORD):boolean;  stdcall;
function GetModLns(lpD:LPDWORD ):boolean;  stdcall;
function PurgeCOM():boolean;  stdcall;
function FlushCOM():boolean;  stdcall;
function GetMaskCOM(lpEvtMask:LPDWORD):boolean;  stdcall;
function SetMaskCOM(EvtMask:DWORD):boolean;  stdcall;
function WaitEventCOM(lpEvtMask:LPDWORD):boolean;  stdcall;
function RxFrame(Too:DWORD;var ADD:byte;var CMD:byte;var N:byte;var Data:array of byte):boolean;stdcall;
function TxFrame(ADDR:byte; CMD:byte; N:byte; Data:array of byte):boolean;  stdcall;
...
implementation

function AccessCOM; external 'wsp32.dll';
function OpenCOM; external 'wsp32.dll';
function CloseCOM; external 'wsp32.dll';
function SetModLns; external 'wsp32.dll';
function GetModLns; external 'wsp32.dll';
function PurgeCOM; external 'wsp32.dll';
function FlushCOM; external 'wsp32.dll';
function GetMaskCOM; external 'wsp32.dll';
function SetMaskCOM; external 'wsp32.dll';
function WaitEventCOM; external 'wsp32.dll';
function RxFrame; external 'wsp32.dll';
function TxFrame; external 'wsp32.dll';