Tandy 1000 Technical Reference Manual

Tandy 1000
8255A18255A·5
Input Control Signal Definition
Technical Reference Manual
STS (Strobe Input). A "low" on this input loads data into
the input latch.
IBF (Input Buffer Full F/F)
A "high" on this output indicates that the data has been
loaded
into the input latch; in essence, an acknowledgement
ISF is set by STB input being low and is reset by the rising
edge
of the RD input.
INTR (Interrupt Request)
A "high" on this output can be used to interrupt the CPU
when
an input device is requesting service. INTR is set by
the STB
is a "one", IBF is a "one" and INTE is a "one".
It is reset by the falling edge of RD. This procedure allows
an input device to request service from the CPU by simply
strobing
its data into the port.
INTE A
Controlled by bit set/reset of PC 4
INTE B
Controlled by bit set/reset of PC2.
2
PCb) ----/-- I/O
---_c
Figure 8. MODE 1 Input
_________ --+--J/~
STS
!~
________ ..J
I S IT ~ ...
I
\!
-~~.---
\"""---,.....-.------'1'-
~~~~:HFE~~~ - - - -{'----------tl-~>- ------------------- --
Figure 9. MODE 1 (Strobed Input)
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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