CS4237B Datasheet, PDF (60/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
GAME PORT INTERFACE
The Game Port logical device software interface
utilizes 10-bit address decoding and is located at
PnP address ’GAMEbase’. 10-bit addressing re-
quires that the upper address bits be 0 to decode
a valid address, i.e. no aliasing occurs. For back-
wards compatibility, the Game Port consists of 8
I/O locations where the lower 6 alias to the same
location, which consists of one read and one
write register.
Plug and Play configuration capability will allow
the joystick I/O base address, GAMEbase, to be
located anywhere within the host I/O address
space. Currently most games software assume
that the joystick I/O port is located at 200h.
A write to the GAMEbase register triggers four
timers. A read from the same register returns
four status bits corresponding to the joystick fire
buttons and four bits that correspond to the out-
put from the four timers.
A button value of 0 indicates the button is
pressed or active. The button default state is 1.
When GAMEbase is written, the X/Y timer bits
go high. Once GAMEbase is written, each timer
output remains high for a period of time deter-
mined by the current joystick position. The
number in parenthesis below is the joystick con-
nector pin number.
GAMEbase+0 - GAMEbase+5
D7 D6 D5 D4 D3 D2 D1 D0
JBB2 JBB1 JAB2 JAB1 JBCY JBCX JACY JACX
JACX
Joystick A, Coordinate X (pin 3)
JACY
Joystick A, Coordinate Y (pin 6)
JBCX
Joystick B, Coordinate X (pin 11)
JBCY
Joystick B, Coordinate Y (pin 13)
JAB1
JAB2
JBB1
JBB2
Joystick A, Button 1 (pin 2)
Joystick A, Button 2 (pin 7)
Joystick B, Button 1 (pin 10)
Joystick B, Button 2 (pin 14)
Two bits, JR1 and JR0, are located in the Con-
trol register space (CTRLbase+0) for defining
the speed of the Game Port Interface. Four dif-
ferent rates are software selectable for use with
various joysticks and to support older software
timing loops with aliasing (roll-over) problems.
GAMEbase+6
D7 D6 D5 D4 D3 D2 D1 D0
res res res res res res res res
res
Must not write any value to this
register. May read any value.
GAMEbase+7
D7 D6 D5 D4 D3 D2 D1 D0
res res res res res res res res
res
Must not write any value to this
register. May read any value.
The Game Port hardware interface consists of
8 pins that connect directly to the standard game
port connector. Buttons must have a 4.7 kΩ pul-
lup resistor and a 1000 pF capacitor to ground.
X/Y coordinates must have a 5.6 nF capacitor to
ground and a 2.2 kΩ series resistor to the appro-
priate joystick connector pin. For a detailed
hardware description, see the Reference Design
Data Sheet.
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DS213PP4