Commodore Amiga Hardware Reference Manual page 283

25 RESB* 0 n* Amiga
system
reset.
n* : See warning above
SERIAL INTERFACE CONNECTOR TIMING
Max.iJnum operating frequency is 19.2 KHz. Refer to EIA standard
RS-232-C for operating and installation specifications.
A rate of 31.25
KHz
will
be
supported through
the
use of a MIDI adapter.
Modem control signals (CTS, RTS, DTR, DSR, CD) are collpletely under
software control. The modem control lines have no hardware affect
on and are COIIpletely asynchronous to TXD and RXD.
SERIAL INTERFACE CONNECTOR ELECTRICAL CHARACTERISTICS
OUTPUTS MIN TYP MAX
Vo(-) :
-2.5 -x-
-5.5
V Negative output voltage range
0/0
(+) : 8
-x- 13.2
V Positive output voltage range
10:
-x- 10
ma
Output current
INPUTS MIN TYP
MAX
Vi(+) : 3 -x- 25
V Positive input voltage range
Vi (-) : -25 -x- .5
V Negative input voltage range
Vhys: -x- l -x-
V Input hysteresis voltage
Ii: .3 -x- 10
ma Input current
Unconnected inputs are interpreted
the
same as positive input
voltages.
GAME CONTROLLER INTERFACE CONNECTOR SPECIFICATION
The two 9-pin D-type connectors with pins (male) at the right of the
Amiga nearer the front are used to interface to four types of devices:
1. Mouse or trackball, 3 buttons max.
2. Digital joystick, 2 buttons max.
3. Proportional (pot or proportional joystick), 2 buttons max.
4. Light pen, including pen-pressed-to-screen button.
The connector pin assignments are discussed in sections organized
by similar hardware and/or software operating requirements as shown
in the previous list. Signal names follow those used elsewhere
in this appendix, when possible.
Jll is
the
right controller port connector (JOY1DAT, POT1DAT).
J12 is the left controller port connector (JOYODAT, POTODAT).
NOTE: While most of the hardware discussed below is directly
accessible, hardware should be accessed through ROM kernel software.
This will keep future hardware changes transparent to the user.
GAME CONTROLLER INTERFACE TO MOUSEjTRACKBALL QUADRATURE INPUTS
A mouse or trackball is a device that translates planar motion into
pulse trains. Quadrature techniques are E!IIJlloyed to preserve the
direction as well as magnitude of displacement. The registers JOYODA!
and JOY1DAT
become
counter registers, with y displacement in the hig}".
byte and x in
the
low byte. Movement causes
the
following action:
Up.
Down:
Right:
Left.
y decrements
y increments
x increments
x decrements
To determine displacement, JOYxDAT is read twice with corresponding x
and y values subtracted (careful, modulo 128 arithmetic). Note that
i f either count changes by more than 127, both distance and direction
become ambiguous. There is a relationship between the sallpling
interval and the max.iJnum
speed
(that is, change
in
distance) that
can
be
resolved as follows:
Velocity
<
Distance(max) / SallpleTime
Velocity
<
SQRT(DeltaX**2
+
DeltaY**2) / SampleTima
For an Amiga with a 200 count-per-inch mouse sallpling during eacl:
vertical blanking interval,
the
max.iJnum velocity in either
the
X or Y
direction
becomes:
Velocity
<
(128 Counts * 1 inch/200 Counts) / .017 sec
=
38 in/sec
which should be sufficient for most users.
NOTE: The Amiga software is designed to do mouse update cycles during
vertical blanking. The horizontal and vertical counters are always
valid and may be read at any time.
CONNECTOR PIN USAGE FOR MOUSEjTRACKBALL QUADRATURE INPUTS
PIN MNEMONIC DESCRIPTION HARDWARE REGISTERjNOTES
1 V Vertical pulses JOY[O/l]DAT<15:8>
2 H Horizontal pulses JOY[O/l]DAT(7:0>
3 VQ
Vertical quadrature pulses JOY[O/1]DAT<15:8>
4 HQ
Horizontal quadrature pulses JOY [0/1] DAT<7:0>
5 UBUT*
Unused mouse button See Proportional Inputs.
6 LBUT*
Left mouse button See Fire Button.
7
+5V 125ma max, 200ma surge Total both ports.
8
Ground
9
RBUT*
Right mouse button See Proportional Inputs..