The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

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+0 Contains the last character entered.
+1 Contains the repeat time check which is the system's timer value that when
reached will result in a repeat of the last character if the keycode scanned
has not changed.
+2 Contains the waiting time in timer units that must transpire before a
character can initially be repeated. This value is altered by SETKI (W=dd).
+3 Contains the repeat rate in timer units. This value is altered by SETKI
(R=dd).
3.6.2 Video driver [system driver assigned to *DO]
All @CTL requests are treated as if they were @PUT requests.
The module name assigned to this driver is "$DO". Its data area includes the following:
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+0 Bits 0-2 contain the number of video lines to protect against scrolling. Bit
3 denotes the action to be taken for character values in the range . If set, the values are treated as displayable characters. If reset,
the values are treated as space compression codes in excess 192 (i.e. 0-63).
Bit 4 will denote the action to be taken for character values in the range
. If set, the value is interpreted as a displayable character. If
reset, the value is treated as a video function code as identified in your
operating system user manual. Bits 5-7 are reserved by the DOS.
+1 Contains the low order address of the cursor. You must use the @VDCTL
SuperVisor to reference the cursor by row,column.
+2 Contains the high order address of the cursor. You must use the @VDCTL
SuperVisor to reference the cursor by row,column.
+3 Contains the character that is currently at the cursor position.
+4 Contains the character code defining the cursor.
3.6.3 Printer driver [system driver assigned to *PR]
The printer driver is transparent to all code values when requested by the @PUT
SuperVisor Call. That means that all values from X'00' through X'FF' (0-255) can be sent
to the printer. The printer driver accepts a function value of X'00' via the @CTL request
to return the printer status. If the printer is available, the Z-flag will be set and the
usual A register status image is an X'30'. If the Z-flag is reset, the accumulator will
contain the four high-order bits of the parallel printer port (bits 4-7).
The module name assigned to this driver is "$PR". There exists no data area within the
printer driver.
3.6.4 Forms Filter [non-resident system filter for forms control]
If the FORMS filter is attached to the *PR device, then various codes are trapped and
used by the filter according to user options as follows:
Code Filter Action
X'0D' Generates a carriage return and optionally a line feed (ADDLF). It will form
feed as required.
X'0A' Is treated the same as X'0D'.
X'0C' Will form feed (via repeated line feeds if soft form feed).
X'09' Will advance to the next tab column.
X'06' Will set top-of-form by resetting the internal line counter to zero.
Other character codes may be altered depending on the user translation option (XLATE).
The FORMS filter's module name is "$FF". Its data area includes the following:
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