Some DISPC registers are termed shadow registers. A shadow register change has no direct effect on the configuration of the DISPC. The registers are shadow registers let software change the values of the registers at any time. When all the registers for a given configuration are into the registers, software must set 1 bit only to validate the configuration. When hardware reaches the end of the current frame and sees that the bit field has been set by software, the new configuration is now the configuration used by the hardware.
Note: As a general rule, all shadow registers are updated with the value of their shadows when:
- The interface is enabled.
- The GO bit field of the pipeline, with which the register is associated, is set and the output sync is active.
The bits enabling the hardware to use the new configuration are:
- DISPC_CONTROL1[5] GOLCD bit for all the registers associated to the LCD1 output, and for all registers of WB and DMA, if the LCD1 channel is captured. The update of the registers of the WB and DMA is further delayed by the DISPC_WB_ATTRIBUTES2[7:0] WBDELAYCOUNTER bit field or done when the next frame is captured (the DISPC_WB_ATTRIBUTES[26:24] CAPTUREMODE bit field must be different from 0). The update of the registers occurs at the VFP start period.
- DISPC_CONTROL1[6] GOTV bit for all the registers associated to the TV output, and for all registers of WB and DMA, if the TV channel is captured. The update of the registers of the WB and DMA is further delayed by the DISPC_WB_ATTRIBUTES2[7:0] WBDELAYCOUNTER bit field or done when the next frame is captured (the DISPC_WB_ATTRIBUTES[26:24] CAPTUREMODE bit field must be different from 0). The update of the registers occurs at the external EVSYNC.
- DISPC_CONTROL2[5] GOLCD bit for all the registers associated to the LCD2 output, and for all registers of WB and DMA, if the LCD2 channel is captured. The update of the registers of the WB and DMA is further delayed by the DISPC_WB_ATTRIBUTES2[7:0] WBDELAYCOUNTER bit field or done when the next frame is captured (the DISPC_WB_ATTRIBUTES[26:24] CAPTUREMODE bit field must be different from 0). The update of the registers occurs at the VFP start period.
- DISPC_CONTROL3[5] GOLCD bit for all the registers associated to the LCD3 output, and for all registers of WB and DMA, if the LCD3 channel is captured. The update of the registers of the WB and DMA is further delayed by the DISPC_WB_ATTRIBUTES2[7:0] WBDELAYCOUNTER bit field or done when the next frame is captured (the DISPC_WB_ATTRIBUTES[26:24] CAPTUREMODE bit field must be different from 0). The update of the registers occurs at the VFP start period.
- DISPC_WB_ATTRIBUTES[0] ENABLE bit for all the registers associated to the WB, if the transfer memory-to-memory is not associated with a channel out.
- The DISPC_CONTROL2[6] GOWB bit and the [5] GOLCD and [6] GOTV bits in the DISPC_CONTROL1/DISPC_CONTROL2 registers, combined with the synchronization event of the channel output selected for write back. This applies to all registers associated with the selected channel out and further delayed by the setting in the DISPC_WB_ATTRIBUTES2[7:0] WBDELAYCOUNT bit field, for all registers of the write back and DMA. The GOWB bit is required to be set only in WB capture mode; it is not required when WB memory-to-memory mode is used.
Note: Before setting the GOLCD, GOTV, or GOWB bits, the user must ensure that the bits are cleared. The hardware resets the bits when the update completes.
Table 11-89 lists the shadow registers. Registers that do not have a mark in any column are not shadowed.
Table 11-89 DISPC Shadow Registers (1) i = 0 to 7
(2) j = 0 to 1