Atari 400 Technical Reference Manual page 235

N1 RAMLO*/TRAMSZ* (0004,3l -- RAM data/test pointer (temporary)
RAMLO+1 contains the LSB of the address to be tested (always
=
0)
and TRAMSZ (same as RAMLO+2) contains the MSS of the address to be
tested. RAMLO+O contains the complemented value of the data
originally contained in the memory location being tested.
Later in the initialization process these variables are used for
totally unrelated functions; but first the value in TRAMSZ is moved
to the variables RAMSIZ and MEMTOP+l.
N2 TSTDAT* (0007,1l -- Test data byte save
TSTDAT contains the oTiginal value of the memory location being
tested.
Diskette/Cassette-Boot
As a part of the Power-up sequence, software can be booted from an
attached disk drive or cassette player as explained in Section 10.
N3 DOSINI (000C,2l -- Diskette-boot initialization vector.
DOSINI contains the disk booted software initialization address
from the beginning of the boot file (see Section 10) whenever a
diskette-boot is successfully completed.
N4 CKEV* [004A,1l -- Cassette-boot request flag
CKEV is an internal flag used to indicate that the console [STARTl
key was pressed during Power-up, thus indicating that a
cassette-boot is desired. CKEV equals zero when no cassette-boot is
requested, and is nonzero when a cassette-boot is requested. The
flag is cleared to zero after a cassette-boot.
N5 CASSBT* [004B, II -- Cassette-booting flag
CASSBT is used during the cassette-boot process to indicate to
shared code that the cassette is being booted and not the diskette.
CASSBT equal to zero indicates a diskette-boot, and nonzero indicates
a cassette-boot.
N6 CASINI [0002,2l -- Cassette-boot initialization vector
CASINI contains the cassette-booted software initialization address
from the beginning of the boot file (see Section 10) whenever a
OPERATING SYSTEM C016555 -- Appendix L
250