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Data Channel

Introduction

Asynchronous Data Handling

Synchronous Data Handling

Clocking

Internal Timing Application

External Timing Applications

Control Signals

Data Channel

Introduction

Six data channels are included with the FastPAD base unit. Five low speed data channel channels, numbered 1 through 5, allow the attachment of synchronous (at rates up to 19.2 kbps) or asynchronous (at rates up to 9.6 kbps) RS-232 devices to the FastPAD. The sixth channel, the High Speed Data Channel, supports synchronous data only, with the capability of speeds up to 64 kbps. The High Speed Data Channel is data channel number 7.

(See Chapter 7 for additional FRAM-01 data channels and speeds.)

Asynchronous Data Handling

Each of the five low speed channels supports the following asynchronous data rates.

300 bps
1200 bps
2400 bps
4800 bps
9600 bps

In asynchronous mode, the data channels default is 8 bits, no parity, and 1 stop bit. Since the 8th bit is considered data, 7 bits plus a parity bit is also passed through. Thus the following data formats are supported:

8 bit, no parity
7 bit, even parity
7 bit, odd parity
7 bit, space parity
7 bit, mark parity

The FastPAD does not check parity. All error detection must be handled by the attached devices.

Synchronous Data Handling

All six data ports can handle synchronous data at the following rates:

1.2 kbps	12 kbps
2.4 kbps	14.4 kbps
4.8 kbps	16 kbps
7.2 kbps	16.8 kbps
8 kbps	19.2 kbps
9.6 kbps

In addition to the rates listed above, the High Speed data channel on the FastPAD can operate synchronously at the following rates:

28.8 kbps	32 kbps
38.4 kbps	48 kbps
56 kbps	64 kbps

At the higher rates, a V.11, V.35, or RS-449 interface adapter card is recommended to ensure error-free operation (See Chapter 5 for details). All synchronous data channels are clear, full duplex and independent of data protocol. Data rates are selected through software via the front panel LCD and push-button controls (see Chapter 9). Each provides a female DB25 connector with a DCE interface.

Clocking

Depending on the type of attached device, the FastPAD can be used with internal timing, external timing. This is accomplished by selecting the proper timing parameters and installing the proper Interface Card kit.

Data input and output to and from the FastPAD is accessed via 25 pin connectors for all data channels as well as the composite channel. Figure 6-1 identifies the pin assignments for the various timing signals.

Figure 6-1: Clocking Pin Assignments

Internal Timing Application

Internal clock applications are normally used when connecting a DTE device to the FastPAD. For internal clocking, the data channel provides two clocks, Transmit Clock (RS-232 equivalent pin 15) is used by the attached device to clock data to the FastPAD, Receive Clock (RS-232 equivalent pin 17) is used by the FastPAD to clock incoming data. When the attached device is a DTE, a straight-through cable is used to connect it to the FastPAD.

Figure 6-2: Attaching to a DTE

External Timing Applications

External clock applications are normally used when connecting a device that can accept Transmit Clock and provide Receive Clock to the FastPAD. Based on this selection, a low speed data channel provides Receive Clock (RS-232 equivalent pin 17) and accepts Transmit Clock (RS-232 equivalent pin 24). In this mode, the attached device accepts the FastPAD data channel clock and loops it back to the FastPAD. When the attached device is a DCE, a crossover cable is used to connect it to the FastPAD data channel.

Figure 6-3: Clocking Pin Assignments

Control Signals

Figure 6-4 illustrates the control signal paths and the relationships between them for each data channel connected over a pair of FastPADs.

Figure 6-4: Data Channel Control Signals

FastPAD data channels are DCE. Five control signals are associated with each data channel. Data Terminal Ready (DTR) and Request To Send (RTS) are both input signals from the attached device. Data Set Ready (DSR), Carrier Detect (CD), and Clear To Send (CTS) are output signals to the attached device. A FastPAD link crosses control signals similar to a crossover cable or null modem.

DTR (Input): Data Terminal Ready on each data channel can be optionally passed through to the remote end as DSR (Data Set Ready). ON/OFF transition of DSR may not coincide with a data boundary.
RTS (Input): Request to Send on each data channel can be optionally passed through to the remote end as CD (Carrier Detect). ON/OFF transition of CD may not coincide with a data boundary.
CTS (Output): Clear to Send on each data channel can be programmed to follow local RTS (Request to Send) with a configurable delay or it can configured as permanently ON or OFF.
DSR (Output): Data Set Ready on each data channel can be programmed to follow remote Data Terminal Ready (DTR). Optionally, DSR can be software configured as permanently ON or OFF.
CD (Output): Carrier Detect on each data channel can be programmed to follow remote Request To Send (RTS). Optionally, CD can be software configured as permanently ON or OFF.

To summarize, for each of the output control signals it is possible to software configure CTS, DSR and CD to a high, a low, or to follow the appropriate input control signal.

For data control signals, ON means the control signal is in a space condition (+12 Vdc). OFF refers to the mark condition (-12 Vdc). ±12 Vdc refers to average voltage levels for space and mark in RS-232.

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Data Channel