Peripheral 1 Register
| Number | $05 |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Sets joystick mode, video frequency and Scandoubler. |
| Bit | Function |
|---|---|
| 7-6 | Joystick 1 mode (LSB) |
| 5-4 | Joystick 2 mode (LSB) |
| 3 | Joystick 1 mode (MSB) |
| 2 | 50/60 Hz mode (0 = 50Hz, 1 = 60Hz, pentagon forces 50hz) (0 after a PoR or Hard-reset) |
| 1 | Joystick 2 mode (MSB) |
| 0 | Enable Scandoubler (1 = enabled for vga, 0 for crt) (1 after a PoR or Hard-reset) |
Joystick modes are as follows:
| Code | Effect |
|---|---|
| %000 | Sinclair Joystick 2 (maps to keys 1,2,3,4,5) |
| %001 | Kempston Joystick 1 (uses port Kempston Joystick ($xx1F / 31)) |
| %010 | Cursor Joystick (maps to keys 5,6,7,8,0) |
| %011 | Sinclair Joystick 1 (maps to keys 6,7,8,9,0) |
| %100 | Kempston Joystick 2 (uses port Kempston Joystick 2, Joystick I/O ($xx37 / 55)) |
| %101 | MD 1 (3 or 6 button joystick port Kempston Joystick ($xx1F / 31)) |
| %110 | MD 2 (3 or 6 button joystick port Kempston Joystick 2, Joystick I/O ($xx37 / 55)) |
| %111 | 111 = User Defined Keys Joystick
* Joysticks can be placed in i/o mode via nextreg 0x0B.
* Programming the user defined keys joystick is done through the ps2 keymap interface on nextreg 0x28, 0x29 and 0x2B:
1. Write 128 to nextreg 0x28
2. Write 0 (left joystick) or 16 (right joystick) to nextreg 0x29
3. Write twelve bytes to nextreg 0x2B in order. The bytes correspond to the twelve buttons on an md pad (MODE=11 X Z Y START A C B U D L R=0)
4. Each byte written identifies a key in the 8x7 membrane; bits 5:3 select the row and bits 2:0 select the column with 111 meaning no action
* In kempston and md modes, excess buttons on a controller not read via ports will generate key input if so programmed
|
since core3.1.4: both joysticks are placed in I/O Mode if either is set to I/O Mode. The underlying joystick type is not changed and reads of this register will continue to return the last joystick type. Whether the joystick is in I/O mode or not is invisible but this state can be cleared either through reset or by re-writing the register with joystick type not equal to 111. Recovery time for a normal joystick read after leaving I/O Mode is at most 64 scan lines.
(since core 3.0) both joysticks set to the same type is now confirmed as valid configuration. The result is combined readings from both joysticks to single output.
"MD" above refers to controllers compatible with SEGA Mega Drive system. The 6 (and 3) button variant is mapped onto Kempston port this way (mirroring XYZ buttons on the ABC buttons, so only 4 distinct buttons are supported) (new mapping since core3.1.4):
| Bit | Joystick action |
|---|---|
| 7 | "start" button (pin 9) |
| 6 | A button (pin 6) |
| 5 | C button (pin 9) |
| 4 | B button (pin 6) |
| 3 | Up (pin 1) |
| 2 | Down (pin 2) |
| 1 | Left (pin 3) |
| 0 | Right (pin 4) |
The pin 6 and 9 reading depends on pin 7 being GND/+5V and it is driven by the FPGA internally (scanning both and building state), the Z80 SW reads final 8bit state from ports 0x1F and/or 0x37 (not driving the pin 7).
(core 3.1.1) the sinclair joystick modes are swapped, "sinclair 2" are keys 1,2,3,4,5 and "sinclair 1" are keys 6,7,8,9,0.