Texas Instruments 990 Operation Manual page 51

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Overlay modules 1, 3, and 4 contain two commands each. The commands resident in the overlay
are printed when the overlay is loaded. Overlay module 4, which is a special overlay (see the
description of the PL command in paragraph 3.4.5), must be loaded with the PL command.
The standard loader is called to load the overlay. If a checksum, tag or I/O error occurs during
loading, control is returned to the monitor and the error message LDOO printed. After the service
routine is loaded, the command is activated. All commands residing in the transient area prior to
the overlay are disabled. If an attempt is made to execute a command that normally resides in
the overlay but is not presently there, an error message of MX03 is printed.
Error messages:
LDOO
LDOI
Example:
.ov
8
!5P""
LA
Invalid checksum, tag or I/O error occurred
during loading.
Invalid load LUNO.
The overlay containing the DP and LA commands is loaded from the device assigned to LUNO
8.
3.4.5 LOAD PROM PROGRAMMER (PL). The Load PROM Programmer command is used to
load the PROM Programmer software module into memory.
Syntax definition:
PL {
t,' ... }
[<Iuno>[{ 0' ... } <bias>]]
Parameters:
luno
bias
Logical unit number of the cassette drive on which the
PROM Programmer (PROMPG)is mounted.
Load addresses for the extended PROMPG program.
Parameter default values:
If luno is not specified, a value of 7 (cassette CS I) is used.
If bias is not specified, the supplied value is IC80
16
(the address immediately following the end of
user memory minus 380
16
to cover the length of the extended PROMPG program).
3-B
Digital Systems Division