lpcware

AHB Arbitration Register

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by rmoss on Wed Sep 12 06:18:25 MST 2012
We have currently in Production the LCP2478 with 7" screen working fine.  There was an issue with screen tear on the screen initially, however after setting up the AHBCFG1 Register on the LPC2478 things work fine.

AHBCFG1       =     (0x0 << 31)     // 31 - reserved
                    | (0x5 << 28)     // 30:28 - Priority for LCD
                    | (0x0 << 27)     // 27 - reserved
                    | (0x1 << 24)     // 26:24 - Priority for USB
                    | (0x0 << 23)     // 23 reserved
                    | (0x2 << 20)     // 22:20 - Priority for AHB1
                    | (0x0 << 19)     // 19: reserved
                    | (0x3 << 16)     // 18:16 EP2 - Priority for GPDMA
                    | (0x0 << 15)     // 15 reserved
                    | (0x4 << 12)     // 14:12 EP1 - Priority for CPU
                    | (0x0 << 11)     // 11 reserved
                    | (0x1 << 8)      // 10:8 default master
                    | (0x4 << 4)      // 7:4 quantum size
                    | (0x0 << 3)      // 3 quantum type
                    | (0x2 << 1)      // 2:1 break burst
                    | 0x0;            // 0  scheduler

Now I am porting the project to the LPC1788 and once again have the screen tear issue using the default AHB Arbitrator Register settings.  Per the LPC1788 User Manual, I have set the Matrix Arbitration register to 0x00000C09.  This improved things greatly, however there is still an occasional screen tear even when sitting idle with one bmp displayed.  I am not using DMA for the screen buffer.

Thanks

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