poke4

poke4 addr4 val

Parameters

• addr4 : the nibble (4 bits) address in RAM to which to write,
• val : the 4-bit value (0-15) to write to the specified address

Description

This function allows you to write to the virtual RAM of TIC. It differs from poke in that it divides memory in groups of 4 bits. Therefore, to address the high nibble of position 0x4000 you should pass 0x8000 as addr4, and to access the low nibble (rightmost 4 bits) you would pass 0x8001. The address should be specified in hexadecimal format, and values should be given in decimal.

Example

-- title:	poke4/peek4 example
-- author:	PaulR
-- script:	Lua

-- This example reads and writes into
-- sprite memory so we can see the
-- effect directly

-- Sprites are stored from address
-- 0x04000 onwards. Memory can be
-- addressed in 8 or 4 bit form so
-- we can access sprite memory as follows:

-- 8 bit address | 4 bit address
-- 0x04000       | 0x08000 (high nibble)
--		 | 0x08001 (low nibble)
-- 0x04001       | 0x08002 (high...)
--               | 0x08003 (low...)


-- write color 5 to first pixel of sprite 0
poke4(0x08000,5)
-- write color 10 to next pixel of sprite 0
poke4(0x08001,10)

function TIC()
	cls(0)

	-- display sprite 0
	spr(0,0,0)
        -- the two pixels set by our poke4
        -- commands are visible

        -- display the 8 bit value stored at 0x04000
	print(peek(0x04000),30,30,4)
	-- prints '165'
	-- ie value of 10 shifted left by 4
	-- into the high nibble (10<<4=160)
	-- plus 5 in the low nibble

	-- show our color values using
	-- 4 bit addressing
	print(peek4(0x08000),30,40,4)
	print(peek4(0x08001),30,50,4)
end

See also: Spritesheet editing example in the examples page