Bootstrap Loader - Xerox 560 Reference Manual

Location
(hex) (dec)
20 32
21 33
22 34
23 35
24 36
25
37
26
38
27 39
28 40
29
41
Hexadecimal
020000A8
o
E000058
22110029
64100023
68000028
OOOO####t
22000010
CCOOO025
CDOOO025
69COO022
Symbol ic form
of instruction
L1, 1
BDR,1
BCR,O 40
L1,0
S10,0 *37
TIO,O *37
BCS,12
34
t#### represents four hexadecimal digits that specify
the load device address as entered by the LOAD
NORMAL command.
Figure 14. Bootstrap Loader
Execution of the bootstrap program causes the following
actions:
1. The first record on the selected peripheral is read into
memrory locations X ' 2A
I
through X ' 3F ' (the previous
contents of general register 0 are destroyed as a re-
sult of executing the bootstrap program in locations
X ' 26 1 through X'29 1
) .
2. After the record has been read, the next instruction
is taken from location X '
2A '
{provided that no error
condition has been detected by the device or the
(lOP).
3. When the instruction in location X ' 2A' is executed,
the unit device and device controller selected for the
load operation can accept a new SIO instruction.
4. Further I/o operations from the load unit may be ac-
complished by coding subsequent I/O instructions to
indirectly address location X'25
1
•
Following the successful completion of the load sequence,
the computer system usually continues execution of the
loaded program and begins issuing messages to the operator
via the I/o system to the System Control Console.
RESET SYSTEM
The RESET SYSTEM command performs the combined func-
tions of the RESET BASIC PROCESSOR and RESET I/OSYS-
TEM commands, as well as the function described below:
1. The system control processor bus interface is initialized.
2. The processor memory bus and processor bus interfaces
are initialized.
3. The system memory units are initialized. This process
does not alter any memory locations.
4. AI
I
interrupt levels are reset to the Disarmed and Dis-
abled state.
5. The system ALARM indicator is cleared.
This command is accepted only when the system is in the
IDLE state.
RESET BASIC PROCESSOR
The RESET BASIC PROCESSOR command initial izes the basic
processor by performing the following:
1.
All bits in the Program Status Words, except the in-
struction address, are reset.
2. The program counter of the BP (register 05) is set to a
value of X'26 1
•
3. The Bf' remains in the IlJLt state until allowed to be-
gin execution at location X'26
1
•
This command is accepted only when the system is in the
IDLE state.
Since all memory requests are inhibited during a reset, the
RESET BASIC PROCESSOR command disrupts any simultan-
eous memory request from the standard I/O system.
RESET I/o SYSTEM
When accepted, the RESET I/O SYSTEM command initial-
izes the lOPs and device controllers of the standard I/o
system. All peripheral devices under control of the system
are reset to the "ready
II
condition and all status, interrupt,
and control indicators in the I/O system are reset. This
command is accepted only when the system is in the IDLE
state. The RESET I/o SYSTEM command does not affect
the External Direct Input/Output (DIO), the BP, or other
non-input/output system elements.
zcttL T
SYSTEM HALT
When the HALT command is entered, the BP ceases to
execute instructions and is forced into the IDLE state; the
RUN indicator on the System Control Panel is extinguished
Control Commands 155