EFM32WG Datasheet, PDF (202/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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Color0 source selection is based on the MASKBLEND bitfield of the EBI_TFTCTRL register. Internal
write data is used for MASKBLEND settings equal to IMASK, IALPHA, or IMASKIALPHA. External write
data is used for MASKBLEND settings equal to EMASK, EALPHA, or EMASKEALPHA. The RGB data
for Color1 is read from either the BANKSEL memory bank or from the EBI_TFTPIXEL1 register as
defined in the COLOR1SRC bitfield of the EBI_TFTCTRL register. The alpha blended result will be
written to the BANKSEL memory bank for external writes or to the EBI_TFTPIXEL register for internal
writes. For transactions involving an external memory device, the automatic transaction translation rules
as described in Section 14.3.11 (p. 185) apply. For example, 1 32-bit wide AHB write to a 16-bit wide
external memory can be used to automatically perform 2 16-bit alpha blending operations into external
memory. Three configurations of data source and destination are supported as described next.
In-place alpha blending into external memory is performed by writing RGB data D to address A
in bank BANKSEL with COLOR1SRC set to MEM and MASKBLEND set to EMASK, EALPHA, or
EMASKEALPHA. Note that in this case the EBI automatically translates the AHB write transaction into
a read-modify-write sequence for the external memory.
EBI In-place Alpha Blending into External Memory
Memory[A] = AlphaBlend(D, Memory[A])
(14.4)
Alpha blending into external memory with a Color1 from register is performed by writing RGB data D
to address A in bank BANKSEL with COLOR1SRC set to PIXEL1 and MASKBLEND set to EMASK,
EALPHA, or EMASKEALPHA:
EBI Alpha Blending into External Memory with Background Color1 from Register
Memory[A] = AlphaBlend(D, EBI_TFTPIXEL1)
(14.5)
Internal alpha blending into register EBI_TFTPIXEL is performed by writing RGB data D to
EBI_TFTPIXEL0 with COLOR1SRC set to PIXEL1 and MASKBLEND set to IMASK, IALPHA, or
IMASKEALPHA. This alpha blending interface is intended for use by both the Cortex-M4 and the
DMA controller. For DMA operation three DMA requests are generated. One DMA request indicating
that EBI_TFTPIXEL0 requires new data, one DMA request indicating that EBI_TFTPIXEL1 requires
new data, and one DMA request indicating that new blended data is available in EBI_TFTPIXEL.
The write into EBI_TFTPIXEL0 triggers the alpha blending operation. If software wants to reprogram
EBI_TFTPIXEL1, then this should be done before the EBI_TFTPIXEL0 write, which triggers the alpha
blending. The status of the internal alpha blending interface can also be read via the TFTPIXEL0EMPTY,
TFTPIXEL1EMPTY, and TFTPIXELFULL bits in the EBI_STATUS register.
EBI Internal Alpha Blending from Registers into Register
EBI_TFTPIXEL = AlphaBlend(EBI_TFTPIXEL0, EBI_TFTPIXEL1)
(14.6)
14.3.17.2 Masking
The masking feature can be used to suppress writes. Instead of the write data, the original background
color of a pixel is kept. Masking is supported for writes to an external device and for writes to internal
register EBI_TFTPIXEL0. The 16-bit data value corresponding to the write data to be masked is defined
in the EBI_TFTMASK register. Masking is always based on 16-bit data and it does not depend on the
RGB mode defined in the RGBMODE bitfield of the EBI_TFTCTRL register. For transactions involving an
external memory device, the automatic transaction translation rules as described in Section 14.3.11 (p.
185) apply. For example, 1 32-bit wide AHB write to a 16-bit wide external memory can be used to
perform masking operations on both 16-bit transactions to the external device. Masking can for example
be used when drawing an icon with rounded corners into an external frame buffer. Such an icon can be
written to the frame buffer using a 2-dimensional copy action. If the color of a pixel outside the rounded
corners is set to match the value defined in the EBI_TFTMASK register, then such a matching data
transfer is suppressed. The resulting image in the frame buffer will keep its original background around
the corners of the icon.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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