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

7.6 SUPERVISOR CALL DETAILS
7.6.1 @ABORT SVC-21
This SVC will cause an abnormal program exit and return to DOS. Any JCL execution in
progress will cease. @ABORT functions by loading the HL register pair with a value of
X'FFFF' and passing control to @EXIT.
Registers Affected: Not applicable.
7.6.2 @ADTSK SVC-29
This SVC will add an interrupt level task pointed to by your Task Control Block (TCB) to
the real time clock task processor Task Control Block Vector Table. The task slot can be
0-11; however, some slots are already assigned to certain functions in the DOS. The SVC,
@CKTSK, can be used to test for slot availability. Slot assignments 0-7 are low priority
tasks, slots 8-10 are medium priority tasks, and slot 11 is a high priority task. Note:
The TCB is a pointer to a word of RAM containing the address of the task driver entry
point and not to the location of your task driver. Detailed interfacing on background
tasks is in Chapter 8, the Appendix, on TASK PROCESSOR.
Registers Affected: AF, HL.
Entry
DE Pointer to your Task Control Block (TCB).
C Contains the task slot assignment number.
7.6.3 @BANK SVC-102
This SVC deals with memory bank use. The top half of the first 64K block is bank 0, and
the second 64K is banks 1 and 2. DOS supports a total of 8 memory banks of 32K each
(numbered 0-7). See Chapter 8, the Appendix, on BANK SWITCHING for programming details
and illustrations. Internally, the DOS makes use of three storage bytes: the BAR contains
the bit-image of Bank Available RAM; the BUR contains the bit-image of Bank Used RAM; and
LBANK$ contains the number (0-7) of the currently resident bank. These storage areas are
not directly accessible to the programmer but are referenced through the SVC functions.
In the interfacing register protocol identified below, register-B passes a function code.
Registers Affected: AF, BC, [HL if a transfer is requested].
Bank Request [optional transfer]
Entry:
B 0
C Bank number (0-7). Optionally set bit-7 to transfer to the address specified
in register pair HL.
HL Optional address to transfer to in the new bank. This option is selected by
setting bit-7 of register-C.
Exit:
B Returns a 0.
C Returns the previously resident bank number (0-7). If a transfer has been
specified (via bit-7 set), bit-7 will remain set.
A Returns any error code if NZ condition.
NZ Bank not there.
Bank Release
Entry:
B 1; Reset bank in C.
C Bank number.
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