VCFG
Register: Video Configuration Register.
((PUB ┆ PRI))
VCFG
Returns: Current value of cog's Video Configuration Register, if used as a source variable.
Explanation
VCFG is one of two registers (VCFG and VSCL) that affect the behavior of a cog's Video Generator. Each cog has a video generator module that facilitates transmitting video image data at a constant rate. The VCFG register contains the configuration settings of the video generator, as shown in VCFG Register table below.
VCFG Register | |||||||||
|---|---|---|---|---|---|---|---|---|---|
VCFG Bits | |||||||||
31 | 30..29 | 28 | 27 | 26 | 25..23 | 22..12 | 11..9 | 8 | 7..0 |
- | VMode | CMode | Chroma1 | Chroma0 | AuralSub | - | VGroup | - | VPins |
In Propeller Assembly, the VMode field through AuralSub fields can conveniently be written using the MOVI instruction, the VGroup field can be written with the MOVD instruction, and the VPins field can be written with the MOVS instruction.
VMode
The 2-bit VMode (video mode) field selects the type and orientation of video output, if any, according to the The Video Mode Field table below. .
The Video Mode Field | |
|---|---|
VMode | Video Mode |
00 | Disabled, no video generated. |
01 | VGA mode; 8-bit parallel output on VPins7:0 |
10 | Composite Mode 1; broadcast on VPins 7:4, baseband on VPins 3:0 |
11 | Composite Mode 2; baseband on VPins 7:4, broadcast on VPins 3:0 |
CMode
The CMode (color mode) field selects two or four color mode. 0 = two-color mode; pixel data is 32 bits by 1 bit and only colors 0 or 1 are used. 1 = four-color mode; pixel data is 16 bits by 2 bits, and colors 0 through 3 are used.
Chroma1
The Chroma1 (broadcast chroma) bit enables or disables chroma (color) on the broadcast signal. 0 = disabled, 1 = enabled.
Chroma0
The Chroma0 (baseband chroma) bit enables or disables chroma (color) on the baseband signal. 0 = disabled, 1 = enabled.
AuralSub
The AuralSub (aural sub-carrier) field selects the source of the FM aural (audio) sub-carrier frequency to be modulated on. The source is the PLLA of one of the cogs, identified by AuralSub's value.
The AuralSub Field | |
|---|---|
AuralSub | Sub-Carrier Frequency Source |
000 | Cog 0's PLLA |
001 | Cog 1's PLLA |
010 | Cog 2's PLLA |
011 | Cog 3's PLLA |
100 | Cog 4's PLLA |
101 | Cog 5's PLLA |
110 | Cog 6's PLLA |
111 | Cog 7's PLLA |
VGroup
The VGroup (video output pin group) field selects which group of eight I/O pins to output video on.
The VGroup Field | |
|---|---|
VGroup | Pin Group |
000 | Group 0: P7..P0 |
001 | Group 1: P15..P8 |
010 | Group 2: P23..P16 |
011 | Group 3: P31..P24 |
100-111 | <reserved for future use> |
VPins
The VPins (video output pins) field is a mask applied to the pins of VGroup that indicates which pins to output video signals on.
The VPins Field | |
|---|---|
VPins | Effect |
00001111 | Drive Video on lower 4 pins only; composite |
11110000 | Drive Video on upper 4 pins only; composite |
11111111 | Drive video on all 8 pins; VGA |
Using VCFG
VCFG can be read/written like other registers or pre-defined variables. For example:
VCFG := %0_10_1_0_1_000_00000000000_001_0_00001111
This sets the video configuration register to enable video in composite mode 1 with 4 colors, baseband chroma (color) enabled, on pin group 1, lower 4 pins (which is pins P11:8).
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