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| The '''Super NES Mouse''' (SNS-016) is a peripheral for the Super NES that was originally bundled with ''Mario Paint''.
| | Three controllers analogous to a computer '''mouse''' are known to be compatible with software for the NES or FC, either directly or through a simple adapter. |
| It can be used with an NES through an adapter, made from an NES controller extension cord and a Super NES controller extension cord, that [[Controller port pinout|connects the respective power, ground, clock, latch, and data pins]].
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| As with the [[standard controller]], the mouse is read by turning the latch ($4016.d0) on and off, and then reading bit 0 or bit 1 of $4016 or $4017 several times, but its report is 32 bits long as opposed to 8 bits.
| | *[[Super NES Mouse]] |
| Bit 0 goes to the standard controller ports on an NES or AV Famicom; bit 1 goes to the Famicom 4-player adapter.
| | *[[Hori Track]] |
| | *[[Subor Mouse]] |
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| Some documents about interfacing with the mouse recommend reading the first 16 bits at one speed, delaying a while, and reading the other 16 bits at another speed, following logic analyzer traces from a Super NES console.
| | [[Category:Pointing devices|*]] |
| However, these different speeds are merely an artifact of the main loop of ''Mario Paint'', and the mouse will give a correct report when read at any reasonable speed.
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| For example, a program could read 8 bits, wait a couple thousand cycles, and then read the other 24.
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| The first byte of the report is all zeroes and may be ignored. The other three bytes are sent most significant bit first:
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| <pre>
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| 76543210 Second byte of report
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| ||||++++- Signature: 0001
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| ||++----- Current sensitivity (0: low; 1: medium; 2: high)
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| |+------- Left button (1: pressed)
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| +-------- Right button (1: pressed)
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| 76543210 Third byte of report
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| |+++++++- Vertical displacement since last read
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| +-------- Direction (1: up; 0: down)
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| 76543210 Fourth byte of report
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| |+++++++- Horizontal displacement since last read
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| +-------- Direction (1: left; 0: right)
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| </pre>
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| The displacements are in [[wikipedia:Signed number representations#Sign-and-magnitude method|sign-and-magnitude]], not [[wikipedia:Signed number representations#Two's complement|two's complement]].
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| For example, $05 represents five mickeys (movement units) in one direction and $85 represents five mickeys in the other.
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| To convert these to two's complement, use [[Synthetic instructions#Negate A|negation]]:
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| <pre>
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| ; Convert to two's complement
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| lda third_byte
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| bpl :+
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| eor #$7F
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| sec
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| adc #$00
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| :
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| sta y_velocity
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| lda fourth_byte
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| bpl :+
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| eor #$7F
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| sec
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| adc #$00
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| :
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| sta x_velocity
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| </pre>
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| The mouse can be set to low, medium, or high sensitivity.
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| To change the sensitivity, send a clock while the latch ($4016.d0) is turned on:
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| <pre>
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| ldy #1
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| sty $4016
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| lda $4016,x
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| dey
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| sty $4016
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| </pre>
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| Some revisions of the mouse's microcontroller [http://problemkaputt.de/fullsnes.htm#snescontrollersmousetwobuttonmouse reportedly] power up in an unknown state and may return useless values before the sensitivity is changed for the first time.
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| A mouse detection routine should cycle through the sensitivities anyway to ensure that the connected device is in fact a mouse.
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| Failure to do so is likely to cause things that are not a mouse to be detected as a mouse, such as half of a Four Score if player 3 or 4 is holding Right.
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| Using more than two mice on an AV Famicom is not recommended for two reasons:
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| * A mouse draws 50 mA, which is much more current than the standard controller draws. Drawing too much current is likely to cause the voltage regulator to overheat. | |
| * Changing player 1's sensitivity also affects player 3's, and changing player 2's sensitivity also affects player 4's.
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| A program that reads the mouse while playing [[APU DMC|DPCM samples]] must proceed very carefully.
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| Sample playback causes occasional double reads on $4016 and $4017, deleting a bit from the stream read back.
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| The re-reading solution that can be used for the [[standard controller]] fails here because each latch pulse sent to a mouse will clear its count of accumulated movement, and there is no known way to reliably detect corrupted data.
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| Only the [[Standard controller#APU DMC conflict glitch|OAM DMA sync trick]] reliably avoids these glitches.
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| A program could read the mouse while using the DMC as a interval timer, as long as the mouse is read in the IRQ handler so that the mouse reading subroutine can avoid the sample fetch.
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| [[Category:Controllers]][[Category:Super NES]]
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