Hp48sx Hardware Registers Document v1.0 From: js12@uk.ac.cam.phx (Julian Taplin) Newsgroups: comp.sources.hp48 Date: 26 Aug 91 00:14:18 GMT This is my list of hardware registers on the HP48, and their uses. It is not by any means complete, but is the best I can manage, compiled from various documents and source codes obtained from seq.uncwil.edu... If anybody else has a more complete list, please post it. #00100h: bits 0-1 control the 4 pixel offset of the display. Useful for smooth scrolling. Bit 2 is also involved here but messes up the scan length. Bit 3 seems to put the machine into a coma #00101h: LSBs of the 5 bit contrast control word. #00102h: bit 0 is the MSB of the contrast. Bits 1 and 3 control the voltage difference across the LCD; this is what you modified. Can't see what bit 2 does. #00103h: bit 3 is also involved in the LCD voltage control. #0010Bh: bit 0,1,2,3: \<-, \->, alpha, and alarm indicators #0010Ch: bit 0,1: busy and I/O indicators; bit 3 must be set for the indicators to be on. #0010Dh, #0010Eh, #0010Fh: 11bit register for baud rate: #600 9600 #400 4800 #200 2400 #000 1200 #00110h: R/W UINTR - UART Interrupt Register: Bit 3: Recv Interrupt flag Bit 2: Recv Interrupt Enable Bit 1: XMit interrupt flag Bit 0: XMit Interrupt Enable #00112h: USTAT: Flag register for uart: Bit 1 RECV Ready, 0 = XMit ready #00114h, #00115h: RECV - UART reciever. Reading gets most recent IO character recieved #00116h, #00117h: XMit - Uart transmitter register - Writing causes serial sending to active IO Port #0011Ah: Bit 3 is trigger bit of I.R. Diode - Latched, so you have to reset it all the time if sampling from IR. Also contains IR Control Bits, but I dunno what they do exactly #0011Ch: Bit 3 = I.R. Led Control #00120h - #00124h: display address base register. Ususally set to #F097Ch (or #F09BC with the equation card installed) but you can change it, to look at any memory you want. Note that you can't read this register, just write to it. Remember to type addresses in backwards. #00125h - #00127: amount of overscan per pixel line #00128h : offset to menu area bitmap, normally 7. #00129h : bits 0-1 control the location of the menu area, normally 3. Don't mess with bit 2, which can totally remap your calculator's display! ON-C does not fix what happens, but turning it off does, strangely enough. ---------------------------------------------------------------------------- Julian Taplin |Home of <>! 35 Shelly Garden, CAMBRIDGE, ENGLAND |Retirement home for all old, tired, (0223) 324815 |and generally dead hardware! ----------------------------------------------------------------------------