Remote-processing RPC-30 Manual de usuario descargar pdf (Pagina 17)

CHAPTER 4 SERIAL PORTS

RPC-30 Page 15

Figure 4-3 Data packet

ACCESSING SERIAL BUFFERS

You can access C OM1 and COM 2 buffers in three w ays:

1. INPUT statement. This removes all characters in

the buffer up to the term inator cha racter and puts

them into a variable.

When using the INPUT statement, program

execution is suspended until a < cr> (Enter key) is

received. W hether this is a problem depends on

your particular application.

INPUT strips bit 7 on the COM1 port. This means

ASCII characters from 0 to 127 are received. The

INPUT statement can return a maxim um string

length of about 150 characters.

2. INKEY$(n) function. Characters ar e removed one

at a time. A null string is returned when the buffer

is empty.

In this mode, you have access to the full 256 bytes.

If you don' t read the buffer an d the buffer fills, all

subsequent characters are discarded. INKEY$(n)

may be used anywhere in the program.

3. COM$(n) retrieves all characters in the buffer,

including < cr> ' s and other control co des. This

function is commonly used with ON COM$

multitasking statement. You can retrieve 128 of the

256 bytes in the serial buffer at one time.

SERIAL PORT FILE NUMBERS

CAM BASIC references the ser ial I/O ports by file

numbers, similar to DOS. The following table shows

the corresponding file number to serial I/O port and how

they are used with the various ports.

Description File Examples

COM1 1 PRINT "Hello"

PRINT #1," Hello"

INPUT A$

INPUT #1,A$

A$ = INKEY$(1)

COM2 2 PRINT #2," Hello"

INPUT #2,A$

A$ = INKEY$(2)

COMMANDS

The following is a list of CAMBASIC commands used

for serial I/O. Variations for many commands not listed

here. These commands and functions are ex plained in

the CAM BASIC Program ming M anual.

Command Function

CLEAR COM$ Clears serial input buffer

COM$ Returns string from buffer

CONFIG BAUD Sets serial port parameters

CONFIG COM$ Configures port for ON

COM $(n) interrupt

INKEY$ Returns a character from the

serial buffer

INPUT Receives string from port

LIST Outputs program listing

ON COM$ Calls subroutine on serial

input

PRINT Outputs data in various

formats

TAB Tabs to predetermined

positions

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 37 38

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