SECTION 6
Conversions and Interfaces
PEN*KEY
R
6200/6300 Hand-Held Computer Programmer’s Reference Guide 6-25
Queues
A queue is an 8Ćbyte variable for message passing between tasks. A queue must
be initialized to empty by calling the queue initialization function. A task can
perform three queue operations: post, pend, and accept.
Posting is the action of adding a new message node to a queue. A message node
consists of an 8Ćbyte field (manipulated by int15) followed by a message field.
The length and structure of the message field is left up to the user. Queues differ
from mailboxes in that posting to a nonempty queue just adds a new node to the
tail of the queue.
When a task pends on an empty queue, the task is moved to the pended list until
another task posts to the queue. When a task pends on a nonempty queue, the
pend request returns immediately without pending.
A task can accept from a queue if it wants to retrieve a message from the queue
without pending. An accept from an empty queue returns 0.
Interrupts Supported by 4000API.EXE
The 4000 Series interrupts supported by 4000API.EXE are matrixed into the
entire set of interrupts. These interrupts for 4000API.EXE with its symbolic
notation,
4000API
, are listed in the
Interrupt Definitions
paragraph, starting on
page 6Ć30. Also, see the
Interrupt Index
(in the
Index
section, at the end of this
publication) to locate interrupts alphabetically. 4000API.EXE supports
interrupts in the following table. Remember 4000API can be configured (by the
use of certain switches) to
ignore
specific interrupts:
Table 6Ć2
4000API Interrupts Supported
INT # 4000API Interrupts
Register Values
10h
Display Services
Video Screen Off/On, Alternative Settings
AH=12h BL=36h
Read/Write Contrast, Alternative Settings
AH=12h BL=FEh
Backlight Off/On, Alternative Settings
AH=12h BL=FFh
14h
Serial Communications Services
Initialize COM Port
AH=00h
Send a Character
AH=01h
Receive a Character
AH=02h
Get Port Status
AH=03h
Extended Initialize
AH=04h
Extended Port Control
AH=05h
Port Power Off/On
AH= FFh
6. Conversions and
Interfaces
