The PROTOCOL command sets data line transmission characteristics and protocols for all serial input/output lines. PROTOCOL includes several functions formerly performed by the BAUD, TA-ON/OFF, X-ON/OFF, and MODEM-ON/OFF commands.
Format
PROTOCOL line [baud] [parity] [bits] [[–] D] [[–] XI] [[–] XO] [[–] W] [[–] B] [[–] C] [(C)(I)(O)(S)] |
Parameter(s)
The minus sign disables a characteristic. If no sign is present, the characteristic is enabled.
Parameters can be any of the following and can be entered in any order, separated by spaces or commas. Each parameter is described in detail on the following pages.
line |
Number of the serial line. |
baud |
Baud rate. |
parity |
Parity. |
bits |
Number of significant data bits. |
D or R |
Enables or disables the RTS (Ready-To-Send) signal. |
XI |
Enables or disables inward X-ON/X-OFF codes. |
XO |
Enables or disables outward X-ON/X-OFF codes. |
W |
Enables or disables automatic flow of input in the type-ahead buffer. |
B |
Enables or disables the bell signal on input buffer full. |
C |
Enables or disables CTS (Clear-To-Send) signal. |
C={0/1} |
Forces CTS signal low (C=0) or high (C=1). |
Options can be any of the following and can be entered in any order, separated by spaces or commas. . If an option is not appended to the PROTOCOL command, neither the input nor the output buffer will be affected by the command's execution.
C |
Clears local input and output buffers and resets any flags. |
I |
Clears local input buffer and resets any flags. |
O |
Clears local output buffer and resets any flags. |
S |
Changes the current Stop bit on the specified line to the specified bits. |
When the system is initially installed, all lines are set to the default settings, which are:
baud: |
9600 |
parity: |
EVEN |
bits: |
7 |
DTR: |
OFF |
X-in: |
OFF |
X-out: |
OFF |
bell: |
ON |
type-ahead: |
ON |
Description
PROTOCOL can be used to set transmission characteristics for all serial I/O lines on the system.
To display the current line settings, use the LIST-LINE-CHARS command (or its synonym, LLC).
Baud Rate
Any of the following baud rates can be entered:
50 |
75 |
110 |
134 |
150 |
200 |
300 |
600 |
1200 |
1800 |
2400 |
4800 |
9600 |
19200 |
38400 |
NOTE |
Check if I/O boards and terminals operate at the baud rate selected. |
Parity
Set the parity by entering the letter code for any of the following types:
E |
EVEN |
M |
MARKING |
N |
NONE |
O |
ODD |
S |
SPACE |
Data Bits
The number of significant data bits is set to 7 by default. It can be changed to 5, 6, or 8.
RTS (R, –R) |
The Ready-To-Send (RTS) protocol is used to enable hardware flow control and works the same way as the MODEM-ON/OFF commands. RTS signals are sent from peripheral devices to the system to start and stop transmission of data. If the RTS protocol is enabled, each time the RTS signal goes high, data is transmitted; each time the signal goes low, data transmission stops. If RTS is disabled, the system ignores any RTS signal.
To enable RTS: |
R or D |
To disable RTS: |
-R or –D |
X-ON/X-OFF Protocol
The PROTOCOL command lets you manipulate the software flow control by setting both the inward and the outward X-ON/X-OFF protocols.
Automatic (Inward) X-ON/X-OFF (XI, –XI)
If automatic, or inward, X-ON/X-OFF is enabled, the system automatically sends an X-OFF (CTRL+S) signal to the peripheral device if the type-ahead buffer becomes more than two-thirds full. This prevents the device from transmitting any more input to the system. When the type-ahead buffer becomes less than one-third full, the system automatically sends an X-ON (CTRL+Q) signal, allowing input to resume.
To enable inward X-ON/X-OFF: |
XI |
To disable inward X-ON/X-OFF: |
–XI |
User-controlled (Outward) X-ON/X-OFF (XO, –XO)
The user-controlled, or outward, X-ON/X-OFF protocol works the same way as the X-ON/X-OFF commands. If the user-controlled X-ON/X-OFF is enabled, you can stop terminal output by pressing CTRL+S. You can start it again by pressing CTRL+Q. If outward X-ON/X-OFF is disabled, these control key signals will not work.
To enable outward X-ON/X-OFF: |
XO |
To disable outward X-ON/X-OFF: |
–XO |
Type-ahead Wrap (W, –W)
If type-ahead wrap is enabled: when the type-ahead buffer fills up, any more characters entered into it will push out the first characters entered. Thus the buffer always holds the 127 most recently entered characters.
If type-ahead wrap is disabled: when the type-ahead buffer fills up, no more characters can be entered into it.
To enable type-ahead wrap: |
W |
To disable type-ahead wrap: |
-W |
Bell (B, –B)
If the bell is enabled, a bell signal is sent whenever the type-ahead buffer is full; if the bell is disabled, no signal is sent. Nothing more can be sent on the line until the information in the type-ahead buffer is processed.
To enable the bell: |
B |
To disable the bell: |
-B |
The bell character may be set to B=<ii>, where ii equals an ASCII hexadecimal character in the range of 01 through FE, which defines the character sent when the input buffer is full. The default bell signal is B=<07>.
Alternate Break Key (BK)
The Alternate Break Key, BK=<ii>, defines a hexadecimal character (in the range of 00 through FE) which upon receipt, causes the operating system to act as though it had received a break on the line. To turn the feature off, omit the hexadecimal code, as in the default. The default Alternate Break Key is B=<> or BK=<00>.
NOTE |
This function may be used in addition to the existing Break Key. |
CTS (C, –C)
The Clear-To-Send (CTS) signal is sent from the system to peripheral devices when the system is ready to receive data. If the CTS protocol is enabled, each time the CTS signal goes high, the system is ready to receive data; each time the signal goes low, the system is not ready to receive data. If CTS is disabled, the system ignores any CTS signal.
To enable CTS: |
C |
To disable CTS: |
–C |
Using PROTOCOL
The following example shows the simplest form of the PROTOCOL statement. It sets the baud rate for line 3 to 19,200 baud.
>PROTOCOL 3 19200 |
The next example sets the parity for line 5 to EVEN, the number of bits to 8, enables DTR detection, disables the bell code, and clears the type-ahead buffer:
>PROTOCOL 5 E 8 D –B (C) |
The next example sets the baud rate for line 3 to 9600, enables both inward and outward X-ON/X-OFF protocols, and enables type-ahead wrap:
>PROTOCOL 3 9600 XI XO W |
NOTE |
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