Difference between revisions of "Kempston Joystick 2, Joystick I/O"

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{{Port
 
{{Port
 
|Number=$xx37
 
|Number=$xx37
−
|ShortDesc=Reads movement of joystick using Kempston interface (second joystick variant).
+
|NumberDec=55
−
|PortMask=%---- ---- 0011 0111
+
|ShortDesc=Kempston interface second joystick variant and controls joystick I/O.
 
|Readable=Yes
 
|Readable=Yes
−
|Writable=No
+
|Writable=Yes
 
|Subsystem=Input
 
|Subsystem=Input
 
}}
 
}}
 +
For READ functionality the details are identical with {{PortNo|$xx1F}}
 +
 +
Since core3.1.5 there is option to do I/O operations through joystick ports.
 +
 +
The I/O mode should be set by writing this port first followed by enabling I/O mode on the joysticks with a write to {{NextRegNo|$05}}.
 +
 +
The WRITE functionality:
 +
{| class="wikitable"
 +
! Bit !! Function
 +
|-
 +
| 7-6 || select I/O mode: %00 = bit bang, %01 = clock, %10 = uart
 +
|-
 +
| 5 || Reserved must be 0
 +
|-
 +
| 4 || 0 to read "input" part of I/O from left joystick socket, 1 to read from right joystick socket
 +
The program can still change the active joystick via bit 4 of port 0x37 at any time but for uart mode this should be done during a quiet time in communication.  Any output always appears on pin 7 of both joystick connectors.
 +
|-
 +
| 3-1 || Reserved must be 0
 +
|-
 +
| 0 || parameter bit controls state of pin 7 on both joystick connectors:
 +
bit bang: bit 0 is copied to pin 7<br>
 +
clock: 0 = place slow clock on pin 7 (Fsys/2048 = 13.672kHz), 1 = place fast clock on pin 7 (Fsys/8 = 3.5MHz) &dagger;<br>
 +
uart: 0 = redirect esp uart to joystick connector, 1 = redirect pi uart to joystick connector (Tx appears on pin 7, Rx taken from pin 9)
 +
|}
 +
 +
&dagger; A runt clock pulse may appear in the first cycle, minimum pulse width is 1/Fsys = 35.7ns

Latest revision as of 11:15, 4 May 2020

Number $xx37
Decimal 55
Short desc. Kempston interface second joystick variant and controls joystick I/O.
Bit Mask
Readable Yes
Writable Yes
Subsystem Input

For READ functionality the details are identical with Kempston Joystick ($xx1F / 31)

Since core3.1.5 there is option to do I/O operations through joystick ports.

The I/O mode should be set by writing this port first followed by enabling I/O mode on the joysticks with a write to Peripheral 1 Register ($05).

The WRITE functionality:

Bit Function
7-6 select I/O mode: %00 = bit bang, %01 = clock, %10 = uart
5 Reserved must be 0
4 0 to read "input" part of I/O from left joystick socket, 1 to read from right joystick socket

The program can still change the active joystick via bit 4 of port 0x37 at any time but for uart mode this should be done during a quiet time in communication. Any output always appears on pin 7 of both joystick connectors.

3-1 Reserved must be 0
0 parameter bit controls state of pin 7 on both joystick connectors:

bit bang: bit 0 is copied to pin 7
clock: 0 = place slow clock on pin 7 (Fsys/2048 = 13.672kHz), 1 = place fast clock on pin 7 (Fsys/8 = 3.5MHz) †
uart: 0 = redirect esp uart to joystick connector, 1 = redirect pi uart to joystick connector (Tx appears on pin 7, Rx taken from pin 9)

† A runt clock pulse may appear in the first cycle, minimum pulse width is 1/Fsys = 35.7ns

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