Advanced Communication Board Developer Toolkit 

ABSTRACT:  POLL3.C

POLL3.C is a polled mode BISYNC terminal program. This program uses the ASCII
character set for BISYNC control characters. The base address is 238 Hex and
additional jumpers for the external clock are needed. To build the program,
the ACB.C file must be built/included from the \LIBRARY directory. The program will
terminate when the "Esc" key is typed from the keyboard. POLL3 will transmit
at 4800 bps and receive at the frequency of the RxC clock input. Please
remember that this is a polled program and it does have maximum data rate
limitations. For high speed examples please refer to the DMA and interrupt
driven examples.

Cables:

For BISYNC mode, transmit, receive, Tx Clock, and Rx Clock are needed. The
program may be used in a stand alone loop-back configuration, or with another
PC with an ACB or BISYNC adapter installed. For most ACB adapters use TSET or
TT for an output clock and RxC as an input clock. Please note that TSET
(Transmit Signal Element Timing) is the EIA-530 equivalent of TT, the RS-232
signal Terminal Timing. For a loop-back plug connect the Transmit signal(s)
to the receive signal(s) and the TSET (EIA-530) or TT (RS-232) signal(s) to
the RxC signal(s).

  For Loop-Back Plug:

     For Single Ended (RS-232, MIL-188/114)
	Connect Tx to Rx
	Connect TSET or TT to RxC

     For Differential Interface (RS-530, V.35, MIL-188/C, etc.)
	Connect Tx+ to	Rx+
	Connect Tx- to	Rx-
	Connect TSET+ or TT+ to RxC+
	Connect TSET- or TT- to RxC-

  Point to Point Cable:

     For Single Ended (RS-232, MIL-188/114)
	Connect Tx at point A to Rx at point B
	Connect TSET or TT at point A to RxC at point B
	Connect Tx at point B to Rx at point A
	Connect TSET or TT at point B to RxC at point A

     For Differential Interface (RS-530, V.35, MIL-188/C, etc.)
	Connect Tx+ at point A to Rx+ at point B
	Connect Tx- at point A to Rx- at point B
	Connect TSET+ or TT+ at point A to RxC+ at point B
	Connect TSET- or TT- at point A to RxC- at point B
	Connect Tx+ at point B to Rx+ at point A
	Connect Tx- at point B to Rx- at point A
	Connect TSET+ or TT+ at point B to RxC+ at point A
	Connect TSET- or TT- at point B to RxC- at point A

Dip-Switch and Jumpers:

Note: If a jumper is not listed, that jumper is not relevant to this example.

    ACB-104		ACB-II		    ACB-530
	SW1 2,3,4,8 On	    SW1 1 On		SW1 2,3,4,8 On
	E2 O		    E4 RC TC		E8 0|0000
			    (See Note 1)

    ACB-III		ACB-IV		    ACB-V
	SW2 2,3,4 On	    SW1 2,3,4 On	SW1 2,3,4 On
	E10 |00|	    E2 00||0||00	(See Note 2)
	E6  |0000|

    ACB-VI		ACB-MP		    MAXPORT
	SW1 2,3,4,8 On	    None		SW1 2,3,4,8 On
			    E7 A,B (See Note 3)	(See Note 4)

   Note 1: The ACB-II does not support TSET or TT signal(s). For this card use
	   the TxC signal(s) and set E4 to RC and TC.
   Note 2: The ACB-V can only receive clocks. To use this example you will
	   either need to modify WR11 to receive transmit and receive clocks,
	   or contact technical support for a copy of the modification to
	   allow the ACB-V to source clocks. CCITT V.35 does not specify
	   a clock output.
   Note 3: The modification listed in Note 1 is enabled on the ACB-MP by
	   setting the jumpers on E7 A,B. This is only necessary when the
	   CCITT V.35 interface is selected.
   Note 4: The ACB MAXPORT will not source a clock. To use this example you
	   will need to modify WR11 to receive transmit and receive clocks.



BISYNC Note:

Implementations of BISYNC communications will vary on different computer
systems. It is very possible that you will need to modify this program
to work with another BISYNC application. In most BISYNC applications, the
enter hunt mode command is issued before a link is established. In this
example the enter hunt mode command is issued during initialization. If
the data synchronization is lost, or a new link is desired, press the F1 key.
This will cause the program it issue an enter hunt mode command and begin
searching the data stream for a SYNC character (SYN). This program does not
include a CRC on transmit or receive.

A typical BISYNC message has the following format:

    SYN SYN SOH Header STX Text ETX CRC

Where SYN is sync character, SOH is Start of Header Control Character, Header
is application specific message information, STX is Start of Text Control
Character, Text is the data to be transferred, ETX is End of Text Control
Character (ETB End Text Block can also be used), and CRC is the 16 bit
cyclic redundancy check generated by the SCC and checked by the receiver.
This example program does not send the SOH or Header Information.

BISYNC Communications, unlike SDLC or HDLC, relies on the application or
driver to maintain character synchronization. To ensure data integrity, the
message passing is usually half-duplex (in one direction at a time). Each
node will typically enter HUNT Mode after a message is transmitted. This may
be accomplished in a polling routine or in an Interrupt Service Routine (ISR).
When using the ISR method, the SCC can be programmed to generate and interrupt
on the transition of the SYNC/HUNT bit. Please note that when using BISYNC
communications, the SCC is not aware when character synchronization is lost.
For this reason the Enter Hunt Mode Command must be issued after the
transmission of each message (after the CRC). Please refer to the SCC users
manual for more detailed information on BISYNC Communications.

Build Dependencies:

POLL3.C
 * ACB.OBJ
 * ACB.H
 * Z8530.H
 * ASCII.H (or EBCDIC.H) contains control character #define statements

 * Denotes that files are located in the \LIBRARY directory.