Subor Mouse

A mouse came with Subor's SB2000 famiclone system.

Example games:

• Educational Computer 2000

Input ($4016 write)

7  bit  0
---- ----
xxxx xxxS
        |
        +- Strobe

Output ($4017 read)

7  bit  0
---- ----
xxxx xxxD
        |
        +- Serial data

The mouse returns either 1-byte or 3-byte responses based on the size of the x/y axis movement since the last read. If the movement value for both the X and Y axis is between -1 and 1 (inclusively), the mouse returns a 1-byte response. Otherwise, a 3-byte response is sent. In this case, the strobe bit must be toggled 3 times in a row to read the entire response (e.g read $4017 8 times, toggle strobe bit, read 8 more times, etc.)

1-byte response format

LRXXYY00
||||||||
||||||++- Always 0
||||++--- Y movement (0: no movement, 1 or 2 = went down 1 unit, 3 = went up 1 unit)
||++----- X movement (0: no movement, 1 or 2 = went right 1 unit, 3 = went left 1 unit)
|+------- Right mouse button (1: pressed)
+-------- Left mouse button (1: pressed)

The mouse button order is opposite that of the Super NES Mouse.

3-byte response format

Byte 1

LRSXTY01
||||||||
||||||++- Always 01
|||||+--- Y movement (Bit 4)
||||+---- Y movement direction (1: up, 0: down)
|||+----- X movement (Bit 4)
||+------ X movement direction (1: left, 0: right)
|+------- Right mouse button (1: pressed)
+-------- Left mouse button (1: pressed)

Byte 2

--XXXX10
  ||||||
  ||||++- Always 10
  ++++--- X movement (Bits 0-3)

Byte 3

--YYYY11
  ||||||
  ||||++- Always 11
  ++++--- Y movement (Bits 0-3)

References

• Nocash's EveryNES documentation