Date: Fri, 24 Jul 1998 10:26:35 +0100 From: Roger Hardiman <roger@cs.strath.ac.uk> To: hasty@rah.star-gate.com, rhh@ct.picker.com Cc: multimedia@FreeBSD.ORG Subject: BT848 RISC instructions. Message-ID: <35B8534A.167E@cs.strath.ac.uk>
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Hi, Yong Kim has emailed me about the bt848 RISC instructions for RGB modes and the use of the DMA Split. Please can you help him? Cheers, Roger. Replies to YoosInfo@netsgo.com My problem is that I can't understand about RISC instructions enough. assume that every local register is set for NTSC input and 320*240*3 RGB. now I need to generate a RISC instruction set for that mode. I thought I needed a OP_SYNC and 240 OP_WRITEs like following. OP_SYNC with RESYNC and BKTR_FM1 OP_WRITE with EOL, SOL and 0x03c0 bytes to XXXXXXXX OP_WRITE with EOL, SOL and 0x03c0 bytes to XXXXXXXX . . but bt848 driver doesn't generate such instructions. it generates some different instructions from what I thought. some JUMP codes and WRITE codes that seem stupid. the code generated by bt848 driver is like following. . . OP_WRITE with SOL,EOL and 0x03c0 bytes to XXXXXXXX OP_WRITE with SOL and 0x2c0 bytes to XXXXXXXX OP_WRITE with EOL and 0x100 bytes to XXXXXXXX . . why doesn't the driver move total data of a line to memory at once? is that some kinda optimizing-code to avoid PCI-bus traffic? is it just because there's not enough continued physical memory? what's DMA_BT848_SPLIT (319*2) in your source code? Cheers Roger To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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