5.3 Information about Handshake
This section explains the handshaking system for a serial (RS-232C) interface. If the DXY-1000
series has a processing speed lower than the speed of data transmission, it may miss some data
if preventive action is not taken. To receive all the data perfectly, the DXY-1000 series deter
mines whether data transmission is acceptable according to the remaining capacity of the I/O
buffer. This data transmission system is called a “ handshake” .
The DXY-1000 series supports three handshake modes: hardwire handshake, Xon/Xoff hand
shake and ENQ/ACK handshake.
The hardwire handshake uses the DTR pin of an RS-232C and lets the computer know whether
it is ready to receive data from the DXY-1000 series. Besides this, the DXY-1000 series per
forms handshaking by sending a particular character from the same pin as used for data.
This section will explain the above three handshake modes as well as the software checking
handshake that sends data from the computer using the device control commands while check
ing the remaining buffer capacity of the plotter buffer.
Note:
•In the examples below, a typical BASIC language is used in the concrete programs. Also,
PRINT #1 and INPUT # 1 indicate input and output of data when an RS-232C is used. In this
case, you must have opened the RS-232C port.
♦All character codes (ASCII codes) use decimals.
•Character codes are written in the form CHR$ ( character code).
•Control characters like [ESC] are, for example, written in the form [ESC]CHR$(27). For informa
tion about device control commands, see “ 5.4 Device Control Commands” in Chapter 5.
5.3.1 Hardwire Handshake
The DXY-1000 series has a function to switch the DTR pin of the RS-232C interface from
“ High” to “ Low” according to the remaining buffer capacity. The DTR pin is the No.20 pin
of the RS-232C.
If your computer has a function to stop the output of data when the input is low at the CTS
or DSR pin of the RS-232C, a handshake by the hardware is available. A connection exam
ple for a hardwire handshake is shown in Fig. 5-6. Use this connection for IBM-PCs.
IBM-PC
DXY-1000 SERIES
FG (1)
TXD (2)
RXD (3)
RTS (4)
CTS (5)
DSR (6)
SG (7)
d c d
(8)
DTR
(1)
FG
(2) TXD
(3) RXD
(4) RTS
(5) CTS
(4
) DSR
(7) SG
(8) DCD
(20) DTR
(XY-RS-11,13,31,33)
Fig. 5-6
5 8
Содержание DXY-1100
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Страница 156: ...Roland DIGITAL GROUP ...