RS-232 Parameters – 1

The RS-232 Parameters 1 Parameter Programming Mode contains four of the parameters required for RS-232 communications. From this Parameter Programming Mode the Baud Rate, Parity, Stop Bits and Character Length, and Handshake Options can be selected. The default values are shown in the Red boxes and also in the Parameter Defaults section earlier in this chapter.

Baud Rate

The Baud Rate parameter contains seven selections: 300 Baud, 600 Baud, 1200 Baud, 2400 Baud, 4800 Baud, 9600 Baud, and 19200 Baud. Scan the appropriate Hex 0 through Hex 6 tag to set the desired Baud rate.

Parity

The Parity parameter contains three selections: Odd, Even, and None. For 7-bit characters, bit 8 is the parity bit; for 8-bit characters, bit 9 is the parity bit. Choosing no parity and 7-bit character length causes the scanner to send two (2) stop bits; the scanner must also receive two (2) stop bits. Scan the appropriate Hex 0, Hex 1, or Hex 4 tags to select the desired Parity.

Stop Bits and Character Length

The Stop Bits and Character Length parameter contains four selections: 1 Stop Bit and 7‑bit Character Length, 1 Stop Bit and 8-bit Character Length, 2 Stop Bits and 7-bit Character Length, and 2 Stop Bits and 8-bit Character Length. Choosing no parity and 7‑bit Character Length causes the NCR 7879 to send two (2) stop bits; the scanner must also receive two (2) stop bits. If 8-bit Character length and parity is selected, only one (1) stop bit is sent. Scan the appropriate Hex 0 through Hex 3 tag to set the Stop Bits and Character Length.

Handshake

The Handshake parameter contains six selections. When considering these, note that the scanner controls only RTS; however, it can monitor CTS. The following list identifies each Handshake option.

•RTS is always low, CTS is ignored (Hex 0 tag).

•RTS is always high, CTS is ignored (Hex 1 tag).

•Scanner raises RTS and waits for CTS to go high before transmitting (Hex 2 tag).

•Scanner raises RTS before transmitting and ignores the state of CTS (Hex 3 tag).

•RTS is always low and scanner waits for CTS to go high before transmitting (Hex 4 tag).

•RTS is always high and scanner waits for CTS to go high before transmitting (Hex 5 tag).

Scan the appropriate Hex 0 through Hex 5 tag to set the Handshake option.

Additional Functions

There are other functions associated with RS-232 communications that are not included on the Programming Worksheet. Following are the programming sequences for these functions. Default values are shown in Blue type.

Ignore RS-232 Commands from Host Terminal

Selection	Programming Tag Sequence
Disable	Programming Mode, Hex 7, Hex 0, Hex A, Hex 0, Save and Reset
Enable	Programming Mode, Hex 7, Hex 0, Hex A, Hex 1, Save and Reset