Bus 4 RS232 Port Board (B4serial)

General Description

The Bus 4-Serial Port peripheral provides four bi-directional serial ports. Each port is equipped with an RS-232 driver as well as a TTL- level output for adding RS-485, RS-422 or other adapter modules.

Quick Start

1. Install ADDR jumpers to pins 1-2, 3-4, 5-6, and 7-8 (as shipped).

2. Connect the VAST cable to the SBC2000.

3. Execute the following code:

	GLOBAL temp AS INTEGER
	GLOBAL port AS INTEGER
	CONSTANT crlf AS STRING = "\013\010"
	
	REM Print chars. received on each of
	REM the four B4SERIAL ports
	DO
	   FOR port = 4 TO 7
	      temp = COMM(port,0,0)
	      IF temp <> -1
	         PRINT crlf, port-4, ":", CHR(temp)
	      ENDIF
	   NEXT port
	LOOP UNTIL 0

Software Control

COMM_BUFFER()

Establishes serial buffers for the off-board serial ports COM4 - COM19.

COMM_BUFFER (port AS INTEGER, address AS LONG, size AS INTEGER)

"port"

is the port number of the off-board serial port.

"address"

is the starting address of the buffer.

"size"

is the size of the buffer.

Input buffers collect incoming characters so that an application does not have to get each character from the port before the next one arrives. Vesta Basic does not automatically provide buffers for the ports on the BUS4SERIAL cards; you must use this routine in your application to provide them.

COMM()
The COMM function provides character-level control of the serial ports.

COMM (port, func, value)

The COMM function controls communication on a byte-by-byte level. This COMM() is identical to the Vesta Basic COMM() function used for onboard serial ports 0 and 1. A B4SERIAL peripheral is controlled by COMM() via ports 4 thru 19 in Vesta Basic, or 0 thru 15 in C.

Port Settings for COMM()

In Vesta Basic:

• 4 = COM1 on B4SERIAL serial card 0
• 9 = COM2 on B4SERIAL serial card 2

In C:

• 0 = COM1 on B4SERIAL serial card 0
• 5 = COM2 on B4SERIAL serial card 1

Func Settings for COMM()

MODE()

MODE(port, baud_rate, data_bits, parity, stop bits, timeout)

MODE() Parameters

Interrupts

VMTB allows you to attach up to 4 B4SERIAL boards to a single VAST connector, for ports 4-19.

Each of the four serial ports on the B4SERIAL peripheral has an interrupt request line. The lines are logically OR'ed together and connected to the bus interrupt line, on J1B-6. Since there is no direct way to know which of the four serial ports has generated the interrupt, you will have to read the status registers of each of the ports until you find the one with the request.

The port registers are compatible with the Intel 8250 UART. The register set for each port starts at 0x0000, 0x0010, 0x0020 and 0x0030, respectively.

B4SERIAL Address Jumpers

All jumpers must be installed when using Vesta Basic.

V104 Bus Connector

Com Ports

Each of the four serial ports has two corresponding connectors. The one that has TTL serial levels (labeled 485A-D) connects an RS-485 or other adapter to the board. The other (labeled COM1-4) provides RS-232C serial levels and modem control lines.

The RTS line is used as XMIT_ENABLE when an RS-485 Adapter is installed.

The RXD line is the data-receive pin for each 485 connector. RX0 connects to the RS-232 driver-chip's data-receive output. Data can be received from only one source at a time. Assign the COM port to input by placing a jumper shunt across pins 5 and 6 (RXD & RX0). Select the 485 connector for input by removing the jumper shunt and connecting an RS-485 or other adapter to the connector.

Power Requirements

The current draw for the B4SERIAL with all four serial ports connected to other serial hardware is 40mA. B4Serial Dimension Drawing Dimensions are in inches.

B4SERIAL Dimension Drawing

Dimensions are in inches.

B4SERIAL Schematic page 1

B4SERIAL Schematic page 2