It is often useful to control the memory layout of fields in a data structure to match an interface control definition, or to interface with hardware. Define a data structure matching the RS-232 Plug Definition. Use the 9-pin definition for brevity.

Pin Settings for Plug
(Reverse order for socket.)
__________________________________________
1  2  3  4  5  6  7  8  9  10 11 12 13
 14 15 16 17 18 19 20 21 22 23 24 25
_________________
1  2  3  4  5
6  7  8  9
25 pin                        9 pin
1 - PG   Protective ground
2 - TD   Transmitted data     3
3 - RD   Received data        2
4 - RTS  Request to send      7
5 - CTS  Clear to send        8
6 - DSR  Data set ready       6
7 - SG   Signal ground        5
8 - CD   Carrier detect       1
9 - + voltage (testing)
10 - - voltage (testing)
11 -
12 - SCD  Secondary CD
13 - SCS  Secondary CTS
14 - STD  Secondary TD
15 - TC   Transmit clock
16 - SRD  Secondary RD
17 - RC   Receiver clock
18 -
19 - SRS  Secondary RTS            
20 - DTR  Data terminal ready      4
21 - SQD  Signal quality detector
22 - RI   Ring indicator           9
23 - DRS  Data rate select
24 - XTC  External clock
25 -

MODE RSTWOTHREETWO = BITS;
INT ofs = bits width - 9;
INT 
   lwb rs232           = ofs + 1,
   carrier detect      = ofs + 1,
   received data       = ofs + 2,
   transmitted data    = ofs + 3,
   data terminal ready = ofs + 4,
   signal ground       = ofs + 5,
   data set ready      = ofs + 6,
   request to send     = ofs + 7,
   clear to send       = ofs + 8,
   ring indicator      = ofs + 9,
   upb rs232           = ofs + 9;
 
RSTWOTHREETWO rs232 bits := 2r10000000; # up to bits width, OR #
print(("received data: ",received data ELEM rs232bits, new line));
 
rs232 bits := bits pack((FALSE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE));
print(("received data: ",received data ELEM rs232bits, new line))