Specifications

44 Software Interface
Slot
The DECvoice module provides an environment for the execution of
subsystems. A subsystem is a group of processes that performs a function.
For example, all the processes that translate text to speech are contained
in a subsystem. Each subsystem loaded into the module is associated with
a slot. The slot is used to locate and to identify a particular subsystem for
a particular task.
Each command has a slot field that informs the command processor which
subsystem should process the command. The DECvoice module has a
total of eight slots, 0 through 7. Slot 0 is reserved for the module ROM
and the module system code. Application software can establish which
subsystems are in slots 1 through 7, because the module does not require
any specific assignments for these slots.
If the host sends a command to a slot that is not associated with a
subsystem, the module returns the command with an error indicator in
the command status field. If the host sends a command that has faulty
data, the module returns the command with an error indicator in the
status field. In this case, it is unpredictable what will happen to the
command data.
OP
The OP field contains the subsystem firmware command code. The
command code represents specific firmware commands. Each command
code is specific to a particular subsystem.
For example, sending a code of 0 in the basic subsystem loads a block of
data into the command ring. Zero is the command code for the BASIC_
LOAD command. Sending a code of 0 in the text-to-speech subsystem
causes DECvoice to speak text. Zero is the command code for the SPEAK_
TEXT command.
Status
The status field informs the host whether or not the command was
completed successfully. The module sets this field. For example, if the
command was completed successfully, the module would return a status
code of 0. Any code other than 0 indicates an error.
Data[ ]
This field represents any data that the command operates on. Some
commands do not have a data field.