HP48 SX/GX card port pinouts by Joel Kolstad ---------------------------------------------------------------------- Pins are numbered 1 to 40, going from RIGHT to LEFT as you look at the CONTACTS on a plug in card with the card oriented such that the contacts are on "TOP" of the card, like this: ____________________________ Pin 40 -> /****************************\ (Back of card -- | Top of card ^^^^^^^^ | contacts visible) | | So then... a card inserted into an upright HP-48 has its contacts facing the sky and pin 1 on the left hand side of the calculator. Here are the pin functions: 1 -- Vdd (Power to the card) 2 -- Vbb (Low battery... if the card pulls this low, the 48 will complain about a low battery in the card) 3 -- MA[0] (Memory address from the 48 to the card, LSB) 4..19 -- MA[1]..MA[16] (More memory addresses) 20 -- *WE (When low, the card is being written to) 21 -- CE (Note that conventional RAM chips often use *CE) 22 -- *OE (When low, the card is being read) 23 -- MD[0] (Data line, LSB) 24..30 -- MD[1]..MD[7] (More data lines) 31 -- Not used (SX, GX port 1) -- MA[17] (GX port 2) 32 -- Not used (SX, GX port 1) -- MA[18] (GX port 2) 33 -- XSCL (LCD data clock, LD[0..1] are valid on the falling edge) (SX, GX port 1) -- MA[19] (GX port 2) 34 -- LP (Horizontal sync of LCD display upon falling edge) (SX, GX port 1) -- MA[20] (GX port 2) 35 -- LD[0] (Even column LCD data) (SX, GX port 1) -- MA[21] (GX port 2) 36 -- LD[1] (Odd column LCD data) (SX, GX port 1) -- Not used (GX port 2) 37 -- CDT (Low is a ROM card, high is a RAM card) 38..39 -- Not connected 40 -- Ground Note that the "ground" on the serial port isn't the same as pin 40's ground. In fact, ground on the serial port is really... Vdd! Connecting the two together will most assuredly damage your calculator. Have fun, and remember that you get to use this information at your own risk. ---Joel Kolstad kolstad@lagally.engr.wisc.edu