85
the existing S-register value are retained when the
BOOT
command is executed and are available to the loaded
program.
Loader execution ends with one of the following halt instructions:
•
HLT 00 — a tape read (parity) error occurred.
•
HLT 11 — a checksum error occurred; A = calculated value, B = expected value.
•
HLT 77 — the end of the file was reached with a successful read.
6.2.4
Tracing and Registers
When a debug log has been established, tracing may be configured by specifying one or more of the reporting level
options:
Option
Reporting Level
CMDS
Controller command initiations and completions
RWS
Tape reads, writes, and status returns
CPU
Words received from and sent to the CPU
IOBUS
I/O bus signals and data words received and returned
The
CMDS
option traces the commands executed by the tape controller. The
RWS
option traces the read, write,
and status commands executed by the controller. The
CPU
option traces words received from (control and write
data) and sent to (status and read data) the CPU. The
IOBUS
option traces the I/O backplane signals and data
received and returned via the interface.
Examples of the trace formats follow:
>>MSC cmds: Unit 0 command 023 (RRF) scheduled, pos = 0, time = 1001
>>MSC cmds: Unit 0 command 023 (RRF) complete
>>MSC rws: Unit 0 read 33 word record
>>MSC rws: Unit 0 tape library status = 1
>>MSC cpu: Command = 000101
>>MSC cpu: Status = 000004
>>MSC iobus: Received data 000000 with signals STC | CLF
>>MSC iobus: Returned data 000020
The Data PCA state contains these registers:
Name
Size
Radix
Action
BUF
16
8
Data buffer
CTL
1
2
Control flip-flop
FLG
1
2
Flag flip-flop
FBF
1
2
Flag buffer flip-flop
DBUF [0:65535]
8
8
Tape record buffer
BPTR
17
10
Buffer pointer
BMAX
17
10
Buffer size for writes
