Measurement-computing Digital232 Uživatelský manuál stáhnout pdf (Strana 40)

Section 3 Command Descriptions

3.18

Data Ready Rn

The

Data Ready

command enables digital input data to be latched and

transmitted out the serial port. When used in conjunction with the

Service Request

function, the

External Data Ready

line can both latch the input data and signal the

host computer that new data is available.

In the default mode (R0) data is read and transmitted out the serial port when the

Digital232 receives an R0 command. In R1 mode, data on an input port is latched on

the transition of a signal applied to the

External Data Ready

(

EDR

) line. At that

same time, the latched data is transmitted out the Digital232’s serial port to the host

computer. If EDR transitions again before the previous

EDR

buffered data has been

formatted for output and sent to an internal serial output queue, the Digital232 will

generate an

EDR Overrun

error and ignore the

EDR

read request.

The

EDR

signal must be at least 1 microsecond wide and should have a rise and

fall time of less than 1.0 microsecond. The

EDR

line defaults to rising-edge sensitive,

but can be changed to falling-edge sensitive with the

Invert

command (

I32

In the R2 mode, serial data is sent to the host every time the last serial terminator

is received. If, for example, the serial terminators selected are CR and LF then data is

read and transmitted on receipt of the LF.

Data is read and transmitted to the serial host computer.

Data is latched on an EDR transition and transmitted to the host.

Data is sent to the host computer after every receipt of the last serial

terminator from the host

Example:

reset the

Digital232

request digital I/O data to be sent to the serial host

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 58 59

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