84PCE:Ports:4000

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Synopsis

Port Number: 4000

Memory-mapped address: E30000

Function: LCD Controller

The ports in this range are for accessing the LCD controller. With these ports, you can configure the LCD DMA address, change the color mode, access the palette, alter the LCD cursor, and possibly other useful things.

Datasheet: http://infocenter.arm.com/help/topic/com.arm.doc.ddi0293c/DDI0293.pdf

The LCD itself appears to be the Giant GPM1421C0. Datasheet: http://beck-oled-lcd-tft-display.de/fileadmin/giant-plus/GPM1421C0.pdf

PL111 Register Summary

Name Base Offset Type TIOS Value Description
LCDTiming0 0x000 R/W 0x00000000 Horizontal Axis Panel Control Register 
TIOS Default:
0x1F0A0338

HBP = 31 (actual =        HBP + 1 =  32)
HFP = 10 (actual =        HFP + 1 =  11)
HSW =  3 (actual =        HSW + 1 =   4)
PPL = 14 (actual = 16 * (PPL + 1) = 240)


Name Base Offset Type Reset Value Description
LCDTiming1 0x004 R/W 0x00000000 Vertical Axis Panel Control Register 
TIOS Default:
0x0402093F

VBP =   4
VFP =   2
VSW =   2 (actual = VSW + 1 =   3)
LPP = 319 (actual = LPP + 1 = 320)


Name Base Offset Type Reset Value Description
LCDTiming2 0x008 R/W 0x00000000 Clock and Signal Polarity Control Register 
TIOS Default:
0x00EF7802

PCD =   2 (actual divisor = PCD + 2 = 4)
BCD =   0
CPL = 239 (actual (TFT) = (CPL + 1) * 1 = 240)
IOE =   1
IPC =   1
IHS =   1
IVS =   1
ACB =   0
CLKSEL = 0


Name Base Offset Type Reset Value Description
LCDTiming3 0x00C R/W 0x00000 Line End Control Register 
TIOS Default:
0x00000000

LEE = 0
LED = 0


Name Base Offset Type Reset Value Description
LCDUPBASE 0x010 R/W 0x00000000 Upper Panel Frame Base Address Register, i.e. LCD VRAM address. Only bits 8-18 have an effect; the address is masked into the 0xD00000-0xD7FF00 range. 
TIOS Default:
0x00D40000


Name Base Offset Type Reset Value Description
LCDLPBASE 0x014 R/W 0x00000000 Lower Panel Frame Base Address Register, N/A 
TIOS Default:
0x00000000


Name Base Offset Type Reset Value Description
LCDControl 0x018 R/W 0x0000 LCD Control Register

This Register controls the operating mode, and the panel pixel parameters

31----------------------------------------------------------------------------------------------0
UNDEFINDED      WTRMRK UN LCDVCMP LCDPWR BEPO BEBO BGR LCDDUAL LCDMONO8 LCDTFT LCDBW LCDBPP LCDEN
000000000000000 0      00 00      0      0    0    0   0       0        0      0     000    0

TIOS Default:
000000000000000 0      00 00      1      0    0    1   0       0        1      0     110    1

UNDEFINDED	= Undefined

WTRMRK		= LCD DMA FIFO watermark level

UN		= Undefined

LCDVCMP		= Generate interrupt at:
		    b00 = start of vertical synchronization
		    b01 = start of back porch
		    b10 = start of active video
		    b11 = start of front porch

LCDPWR		= LCD power enable:
		    0 = power not gated through to LCD panel and CLD[23:0] signals disabled, (held LOW)
		    1 = power gated through to LCD panel and CLD[23:0] signals enabled, (active)

BEPO		= Big-endian pixel ordering within a byte:
		    0 = little-endian ordering within a byte
		    1 = big-endian pixel ordering within a byte

BEBO		= Big-endian byte order:
		    0 = little-endian byte order
		    1 = big-endian byte order

BGR		= RGB or BGR format selection:
		    0 = RGB normal output
		    1 = BGR red and blue swapped

LCDDUAL		= LCD interface is dual-panel STN:
		    0 = single-panel LCD is in use
		    1 = dual-panel LCD is in use

LCDMONO8	= Monochrome LCD. This has an 8-bit interface. This bit controls whether monochrome STN LCD uses a 4 or 8-bit parallel interface. It has no meaning in other modes, and you must program it to zero
		    0 = mono LCD uses 4-bit interface
		    1 = mono LCD uses 8-bit interface

LCDTFT		= LCD is TFT:
		    0 = LCD is an STN display. Use gray scaler
		    1 = LCD is a TFT display. Do not use gray scaler

LCDBW		= STN LCD is monochrome (black and white):
		    0 = STN LCD is color
		    1 = STN LCD is monochrome

LCDBPP		= LCD bits per pixel:
		    b000 = 1bpp
		    b001 = 2bpp
		    b010 = 4bpp
		    b011 = 8bpp
		    b100 = 16bpp
		    b101 = 24bpp (TFT panel only)
		    b110 = 16bpp 5:6:5 mode
		    b111 = 12bpp 4:4:4 mode

LCDEN		= CLCDC enable:
		    0 = LCD signals CLLP, CLCP, CLFP, CLAC, and CLLE disabled (LOW)
		    1 = LCD signals CLLP, CLCP, CLFP, CLAC, and CLLE enabled (HIGH)

To set the LCD to 8bpp (palette mode): 

ld a,$27
ld ($E30018),a

When the LCD is in 8bpp mode, data written to VRAM will act as an 8-bit index to the LCD's 256x16-bit Color Palette. Note that the colour palette must be initialized prior to setting this mode or you will receive unexpected results. (See LCDPalette register - 0x200 for information on the Color Palette).
This will effectively halve the amount of VRAM required to store a full resolution 320x240 image (76800 bytes vs 153600 bytes). The extra 76800 bytes of VRAM could be used to double buffer or for temporary data storage.
Note that the TIOS will not be usable in this mode, it expects 16bpp 5:6:5 mode at all times.

To set the LCD to 16bpp 5:6:5 mode (TIOS default): 

ld a,$2D
ld ($E30018),a


Name Base Offset Type Reset Value Description
LCDIMSC 0x01C R/W 0x0 Interrupt Mask Set/Clear Register


Name Base Offset Type Reset Value Description
LCDRIS 0x020 RO 0x0 Raw Interrupt Status Register


Name Base Offset Type Reset Value Description
LCDMIS 0x024 RO 0x0 Masked Interrupt Status Register


Name Base Offset Type Reset Value Description
LCDICR 0x028 WO 0x0 LCD Interrupt Clear Register 


31---------------------------------------------------------0
UNDEFINED                   MBERROR Vcomp LNBU FUF UNDEFINED
000000000000000000000000000 0       0     0    0   0

MBERROR = AHB master error
Vcomp   = Vertical compare
LNBU    = LCD next base address update
FUF     = FIFO underflow


Name Base Offset Type Reset Value Description
LCDUPCURR 0x02C RO 0x00000000 LCD Upper and Lower Panel Current Address Value Registers


Name Base Offset Type Reset Value Description
LCDLPCURR 0x030 RO 0x00000000 LCD Upper and Lower Panel Current Address Value Registers


Name Base Offset Type Reset Value Description
- 0x034-0x1FC - - Reserved


Name Base Offset Type Reset Value Description
LCDPalette 0x200-0x3FC R/W 0x00000000 256x16-bit Color Palette Registers

The LCDPalette Registers contain 256 palette entries. 

15-----------------0
I  BLUE  GREEN RED
0  00000 00000 00000

I		= Intensity/unused
B		= Blue palette data
G		= Green palette data
R		= Red palette data

The palette can hold 256 x 16-bit colour entries in 1555 format. The 1 bit is the LSB of green. The BLUE and RED values can be swapped via bit-8 of the LCDControl Register.

When 8bpp mode is enabled the LCD will utilize graphics data to index this palette and display the resultant colour - as opposed to interpreting graphics data as colours directly.
Palettes can be very useful for reducing data requirements and increasing display related performance.
To generate and copy a palette of low=high (xLIBC equivilent) colours converted to 1555 format, you can do something similar to: 

CopyHL1555Palette:
	ld hl,$E30200				; palette mem
	ld b,0
_cp1555loop:
	ld d,b
	ld a,b
	and %11000000
	srl d
	rra
	ld e,a
	ld a,%00011111
	and b
	or e
	ld (hl),a
	inc hl
	ld (hl),d
	inc hl
	inc b
	jr nz,_cp1555loop
	ret

With this palette installed, high=low graphics data (from the TI-84+CSE for example) can be reused without the need for conversion. This is because the high=low colour data will now become an index to the converted 1555 palette. Note that there will be a negligible colour difference due to the loss of precision in green.

Name Base Offset Type Reset Value Description
- 0x400-0x7FC - - Reserved


Name Base Offset Type Reset Value Description
CursorImage 0x800-0xBFC R/W 0x00000000 Cursor Image RAM Register


Name Base Offset Type Reset Value Description
ClcdCrsrCtrl 0xC00 R/W 0x00 Cursor Control Register


Name Base Offset Type Reset Value Description
ClcdCrsrConfig 0xC04 R/W 0x0 Cursor Configuration Register


Name Base Offset Type Reset Value Description
ClcdCrsrPalette0 0xC08 R/W 0x000000 Cursor Palette Registers


Name Base Offset Type Reset Value Description
ClcdCrsrPalette1 0xC0C R/W 0x000000 Cursor Palette Registers


Name Base Offset Type Reset Value Description
ClcdCrsrXY 0xC10 R/W 0x00000000 Cursor XY Position Register


Name Base Offset Type Reset Value Description
ClcdCrsrClip 0xC14 R/W 0x0000 Cursor Clip Position Register


Name Base Offset Type Reset Value Description
- 0xC18-0xC1C - - Reserved


Name Base Offset Type Reset Value Description
ClcdCrsrIMSC 0xC20 R/W 0x0 Cursor Interrupt Mask Set/Clear Register


Name Base Offset Type Reset Value Description
ClcdCrsrICR 0xC24 WO 0x0 Cursor Interrupt Clear Register


Name Base Offset Type Reset Value Description
ClcdCrsrRIS 0xC28 RO 0x0 Cursor Raw Interrupt Status Register


Name Base Offset Type Reset Value Description
ClcdCrsrMIS 0xC2C RO 0x0 Cursor Masked Interrupt Status Register


Name Base Offset Type Reset Value Description
- 0xC30-0xDFC - - Reserved


Name Base Offset Type Reset Value Description
- 0xF00-0xF08 - - Programmers Model for Test


Name Base Offset Type Reset Value Description
- 0xF0C-0xFDC - - Reserved


Name Base Offset Type Reset Value Description
CLCDPeriphID0 0xFE0 RO 0x11 Peripheral Identification Register 0


Name Base Offset Type Reset Value Description
CLCDPeriphID1 0xFE4 RO 0x11 Peripheral Identification Register 1


Name Base Offset Type Reset Value Description
CLCDPeriphID2 0xFE8 RO 0x-4a Peripheral Identification Register 2


Name Base Offset Type Reset Value Description
CLCDPeriphID3 0xFEC RO 0x00 Peripheral Identification Register 3


Name Base Offset Type Reset Value Description
CLCDPCellID0 0xFF0 RO 0x0D PrimeCell Identification Register 0


Name Base Offset Type Reset Value Description
CLCDPCellID1 0xFF4 RO 0xF0 PrimeCell Identification Register 1


Name Base Offset Type Reset Value Description
CLCDPCellID2 0xFF8 RO 0x05 PrimeCell Identification Register 2


Name Base Offset Type Reset Value Description
CLCDPCellID3 0xFFC RO 0xB1 PrimeCell Identification Register 3


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