elee24@castle.ed.ac.uk (H Bruce) (07/26/90)
Since this appears to be the only group discussing low cost 8 bit micros here I wish to ask some questions on the choice of uP for a project. The project requires a low cost uP to control a frame grabber and a modem and to process the images. A number of images will be captured, the first frame compressed (using lossless DPCM) for transmission over a modem and then the frame differences will be sent. The images will be approximately 160 by 100 pixels. Current thinking in the group is to choose an 8051 because it * is widely supported (second sourced, high level language compilers) * has a built in UART * has scratch pad RAM * has a hardware multiplier However the 8051 is not ideally suited for accessing external RAM into which the image will be mapped. For image processing functions the pixels in the image may have to be accessed may times. Would a 6809 be any better at this - how long does it a 6809 to read a byte from RAM ? An 8051 running at 12Mhz would take 3us to move a pixel into the accumulator for pixels with a 256 byte block. (5us is both the lo and hi address pointers were loaded each time). I am just worried about using a microcontroller for what I see as a microprocesor application. Thanks for your attention. Henry Bruce
jensting@skinfaxe.diku.dk (Jens Tingleff) (07/27/90)
elee24@castle.ed.ac.uk (H Bruce) writes: >Since this appears to be the only group discussing low cost 8 bit micros here >I wish to ask some questions on the choice of uP for a project. >The project requires a low cost uP to control a >frame grabber and a modem and to process [..] To run of on a tangent: Why not use a low cost 16 bit ptocessor ? The 68000 springs readily to mind.. . I don't think the cost is too extravagant, if you can stay in the slow speeds..., and developement software is *cheap* (compared to dedicated Xassemblers / Xcompilers). If you're designing from scratch, I don't think the problems of PCB/circuit layout are too large. Check the German magazines c't and MC for numerous hardware projects in this league (I see you're in england, so there is a non-zero probability that you can get the German magazines..). Jens Jens Tingleff MSc EE, Institute of Computer Science, Copenhagen University Snail mail: DIKU Universitetsparken 1 DK2100 KBH O "It never runs around here; it just comes crashing down" apologies to Dire Straits