1 line
1.4 KiB
Plaintext
1 line
1.4 KiB
Plaintext
|
con
GP_RIGHT = %00000001
GP_LEFT = %00000010
GP_DOWN = %00000100
GP_UP = %00001000
GP_START = %00010000
GP_SELECT = %00100000
GP_B = %01000000
GP_A = %10000000
var
long stack[6]
long nes_bits
pub start
nes_bits := 0
'cognew(process, @stack)
pub read
'return nes_bits
return process
pub process | i, bits
' set I/O ports to proper direction
' P3 = JOY_CLK (4)
' P4 = JOY_SH/LDn (5)
' P5 = JOY_DATAOUT0 (6)
' P6 = JOY_DATAOUT1 (7)
' NES Bit Encoding
' step 1: set I/Os
DIRA[3] := 1 ' output
DIRA[4] := 1 ' output
DIRA[5] := 0 ' input
DIRA[6] := 0 ' input
repeat
' step 2: set clock and latch to 0
OUTA[3] := 0 ' JOY_CLK = 0
OUTA[4] := 0 ' JOY_SH/LDn = 0
'Delay(1)
' step 3: set latch to 1
OUTA[4] := 1 ' JOY_SH/LDn = 1
'Delay(1)
' step 4: set latch to 0
OUTA[4] := 0 ' JOY_SH/LDn = 0
' step 5: read first bit of each game pad
' data is now ready to shift out
' first bit is ready
' left controller
bits := INA[5] | (INA[6] << 8)
' step 7: read next 7 bits
repeat i from 0 to 6
OUTA[3] := 1 ' JOY_CLK = 1
'Delay(1)
OUTA[3] := 0 ' JOY_CLK = 0
bits := (bits << 1)
bits := bits | INA[5] | (INA[6] << 8)
'Delay(1)
' invert bits to make positive logic and store result
nes_bits := (!bits & $FFFF)
return nes_bits
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