Tandy 1000 Technical Reference Manual

Tandy 1000
Technical Reference Manual
Status Register
The 4-bit "read only" register provides video and light pen status. It is addressed
by a read operation
at 30A. (The video array address register is not used to
select this port.) The following table gives the register's bit functions:
Bit Status
o Display Inactive
1 Light Pen Trigger Set
2 Light
Pen Switch Made*
3 Vertical Retrace
Status Register
Bit 0 When bit 0 is (0), the display is active. When (1), this indicates video
is not displayed.
Bit 1 When bit 1
is "high," this indicates that the light pen input has a
positive-going edge, and
has set the light pen trigger. When this trigger
is "low," during a system power-on, it may be cleared by perform-
ing
an I/O command to address 30B. No specific data is required
due to address-activated action.
Bit 2
Bit 2 is the status of the light pen switch. When bit 2 is "low," the
light pen switch
is on. The switch is not latched or debounced.
Bit 3 When bit 3 is
"high," this indicates that the vertical retrace is active.
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Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200