CHKNCOM represents an an extended version of CHK4COM. 

CC, Vision Systems, 12.09.1996:

The following extensions were implemented:
1. Allows for up to 16 Ports instead of 8
2. New Parameter in .CFG-File: TestRI. If set to 0 disables testing of
   RI Signal in the Loopback-Test. This is needed for Turbo-8Com.
3. New Test: Internal Loopback. The Internal Loopback is tested first in
   each port. When this test fails it is reported immediatly without further
   test of external loopback on the same port. So a report of "External 
   Loopback failure" means that the internal loopback has passed without
   problem, since otherwise it would be reported "internal loopback failure".
4. CHKNCOM will now only test for Ports noted in the config file under
   [Ports]. When 8 Ports are in the [Ports] Section then only 8 Ports will
   be tested.
5. New Irq Vector test: Insert IrqVector=01C2 into the [Address] section of
   CHKNCOM.CFG. CHKNCOM will then test for a IRQ Vector register at the 
   appointed address (in this case 1C2h).

CC, Vision Systems, 20.01.1997:

New extensions to the IRQ vector register test: It is now possible to 
test also irq vector registers for 4-port cards and also for other ports
than COM1..8.
1. To be able to test other than 8-port irq vector registers insert a
   IrqVectorSize=4 line into the [Address] section of CHKNCOM.CFG.
   CHKNCOM will then test for only the given number of ports, even when
   there are more ports installed in the system and COMxBase' are defined
   for more than just the IrqVectorSize number of ports.
2. A new Key "IrqVectorStart" in CHKNCOM.CFG allows the user to select
   the port (COM1=1, COM2=2,...) at wich the irq vector testing starts. 
   This allows for the possibility of any number of COM-ports in the system
   and in "COMxBase" fields that don't belong the the card that hosts the
   irq-vector register.

The following fragement of CHKNCOM.CFG illustrates the above changes:
It will test for 6 COM ports at the addresses 03F8 (COM1), 02f8 (COM2),
0180, 0188, 0190 and 0198. It also will check for correctly functioning
irq vector register at the address 01c2h. The irq vector register is set
to reflect the irq's of ports starting at COM3/COMC/0180h and there are
4 bits active in the irq vector register (4 ports meaning COM3..6, or 
0180h..0198h.
The example fragment:

[Address]
ComABase=03F8
ComBBase=02F8
ComCBase=0180
ComDBase=0188
ComEBase=0190
ComFBase=0198
IrqVector=01C2
IrqVectorStart=3
IrqVectorSize=4

CC, Vision Systems, 20.05.1998:

Program extended to support RS422/RS485 Boards like "VScom 400I Pro". Now
supports new key value "RS422-485" in Group "GENERAL". If set to "0" CHKNCOM 
will function normally. If RS422-485=1, CHKNCOM will NOT test RI, DCD and DSR 
functioning in loopback test because RS422/485 boards do not support them. 
The following example .cfg will test for four serial RS422 ports using standard
addresses and irqs but RS422 mode:

[General]
TestRI= 1
BaudMulti=1
BaudDivis=1
RS422-485=1

[Ports]
Com1Base=3F8
Com2Base=2F8
Com3Base=3E8
Com4Base=2E8

[Address]
ComABase=3F8
ComBBase=2F8
ComCBase=3E8
ComDBase=2E8
IrqVector=300
IrqVectorSize=4
IrqVectorStart=1

[Irq]
ComAIrq=4
ComBIrq=3
ComCIrq=4
ComDIrq=3