From mhardy@acorn.co.uk (Michael Hardy) Thu Dec 2 11:20:43 1993 Path: doc.ic.ac.uk!uknet!acorn!not-for-mail From: mhardy@acorn.co.uk (Michael Hardy) Newsgroups: comp.sys.acorn Subject: Re: Clock on 400/1 Date: 30 Nov 1993 16:19:54 -0000 Organization: Acorn Computers Ltd, Cambridge, England Lines: 75 Message-ID: <2dfrra$5hm@acorn.acorn.co.uk> References: NNTP-Posting-Host: acorn.acorn.co.uk In article gst@dcs.ed.ac.uk (George Taylor) writes: >In article <29149@armltd.uucp> mike@nsict.org writes: > >>So does mine. There was a fix posted for this some time back (involved >>resetting the IIC clock chip manually), but since I stopped being >>@phx.cam.ac.uk, I haven't got it anymore... > >I managed to *obtain* the problem using IIC_Control so be warned! Unfortunately, the RISC OS 2 PRMs got the read/write sense of IIC_Control reversed. This error has more potentially severe side effects than any other we're aware of. We have done our best to publicise this error, and have also corrected it in the RISC OS 3 PRMs. However, for those of you who don't have a copy, here is the correct description of this SWI: ---------------------------------------------------------------------------- IIC_Control (SWI &240) ====================== Control IIC devices On entry -------- R0 = device address (bit 0 = 0 to write, bit 0 = 1 to read) R1 = pointer to block R2 = length of block in bytes On exit ------- R0 - R2 preserved Interrupts ---------- Interrupts are disabled Fast interrupts are enabled Processor Mode -------------- Processor is in SVC mode Re-entrancy ----------- SWI is not re-entrant Use --- This call allows reading and writing to IIC devices. IIC is an internal serial protocol. It is used in RISC OS machines for writing to the clock chip and IIC compatible devices on expansion cards. The possible error is `No acknowledge from IIC device' (&20300). Related SWIs ------------ None Related vectors --------------- None ---------------------------------------------------------------------------- I hope this helps anyone trying to use this SWI. - Michael J Hardy --------------------------+------------------------------------------------- Technical Publications | Email: mhardy@acorn.co.uk Acorn Computers Ltd |------------------------------------------------- Acorn House | Telephone: +44 223 254352 Vision Park | Fax: +44 223 254262 Histon | Telex: 329118 EXECOM G Cambridge CB4 4AE |------------------------------------------------- England | Disclaimer: All opinions are my own, not Acorn's --------------------------+-------------------------------------------------