Page mode is available only for users of screen terminals that can receive, display, and transmit at least three lines of data at a time.
The number of lines a terminal can receive and display is calculated from the PAGESIZE, LINEWIDTH, and MAXOUTPUT attributes of the terminal; the default values for these terminal attributes are defined by the MCP, which gets the terminal configuration information from the data comm software used by the installation, such as the DATACOMINFO configuration, CCF, the terminal emulator, and so on.
For the proper page mode operation, the default terminal attributes must reflect the actual terminal characteristics.
The terminal attributes can be checked and adjusted by the CANDE TERMINAL command. However, any differences between the adjusted values and the default values could result in an undesirable or unpredictable page mode operation.
The display capacity of the terminal equals the smaller of either the PAGESIZE (number of lines received on the terminal screen at a time) or MAXOUTPUT (the number of characters a screen can display and hold in display terminal buffer memory) divided by LINEWIDTH (characters per line):
PAGESIZE= 24 lines MAXOUTPUT= 1000 characters LINEWIDTH= 80 characters
For example, given the previously listed limits, the terminal's display capacity (the size of a page) is 12 lines, which is the smaller of PAGESIZE (24 lines) and MAXOUTPUT divided by LINEWIDTH (1000/80 = 12 lines).
The maximum possible value allowed for MAXOUTPUT is 9180.
MAXINPUT is the number of characters a terminal is capable of transmitting at one time. The maximum possible value allowed for MAXINPUT is 9180. CANDE requests and receives the terminal configuration information from the MCP. The MCP gets the terminal configuration information from the data comm software used by the installation, such as the DATACOMINFO configuration, CCF, the terminal emulator, and so on.. The TERMINAL command is used to list the MAXINPUT (refer to the TERMINAL command in this manual).
CANDE sends a maximum of PAGESIZE*LINEWIDTH characters for each page. To PAGESIZE*LINEWIDTH add the resulting number of characters for the following conditions:
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If WRAPAROUND is FALSE, add (PAGESIZE - 1)*2 characters (for the Carriage Return and Line Feed characters)
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If FORMSCAPABLE is TRUE, add 5 for the five additional characters that are sent.
For example, CANDE sends 1971 characters given the following values for PAGESIZE, LINEWIDTH, WRAPAROUND, and FORMSCAPABLE:
PAGESIZE= 24 lines LINEWIDTH= 80 characters
PAGESIZE*LINEWIDTH =1920 (if WRAPAROUND=F, add (PAGESIZE-1)*2)+46 (if FORMSCAPABLE=T, add 5 characters)+5
Total number of characters sent =1971
A display in page mode can be distorted for the following reasons:
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The data comm buffer size for a terminal is not large enough to accommodate the number of characters CANDE sends. (Refer to the manual for your terminal emulator for an explanation of how to set the data comm buffer size.)
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The CANDE terminal settings do not match the physical characteristics of the device currently in use. The logical device and station characteristics defined in any portion of the data communication system, which may be sensitive to line and page parameters, must match the actual physical characteristics of the device.
Proper page mode operation occurs when all portions of the communications path are in agreement on the page attributes, such as characters per line, lines per page, buffer limits, and so on.
