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

Bank Availability Test
Entry:
B 2; Test if bank C in use.
C Bank number.
Exit:
NZ In use.
Bank Reservation Request
Entry:
B 3; Set bank in C.
C Bank number.
Exit:
NZ Already in use.
What Bank is Resident
Entry:
B 4; Return current installed bank.
Exit:
A Returns the bank number (0-7) of the currrently resident bank.
Note: The coding of the @BANK routine will not return an error if you try to reset
a Bank Used RAM (BUR) that is "in-use" because it is not installed. The way
in which bank-reset should be performed is to know which one you were using
and made in-use. Note that even though @BANK permits you to reset a nonexistant
bank, if you try to enable it, you will get an error since the
enabling routine will not permit the selection of a bank not installed.
7.6.4 @BKSP SVC-61
This SVC will perform a backspace of one logical record in the referenced file.
Registers Affected: AF.
Entry:
DE A pointer to the FCB of the file to backspace.
Exit:
A Error return code.
Z Set if the operation was successful.
7.6.5 @BREAK SVC-103
This SVC is used to establish or reset a key vector. The condition is
observed as a background interrupt task. Once activated, a will pass control to
your vectored routine providing the current program counter is above the resident DOS and
below HIGH$.
Registers Affected: AF.
Entry:
HL Address of your break vector.
HL X'0000' to restore to system break handler.
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