Dynamic Shift Registers - Bitsavers - Trailing-Edge

ROM Code ConvertersMM4230KP/MM5230KPASCII-7 to selectric code convertergeneral descriptionThe MM4230KP/MM5230KP MOSread-only memoryhas been programmed to perform the conversionbetween the American Standard Code forInformation Interchange in seven bits (ASCII)and the Selectric correspondence bail code transmittedand received by the I BM Series 7 input/output printers.application hintsThe ASCII field and Selectric bail code field asdefined do not map exactly: for instance "space"is handled as a normal 7-bit code in ASCII, but ishandled as a unique switch and solenoid pair in theSelectric printer. And even among the graphiccharacters, ± and rf. exist only for Selectric, and>and < only for ASCII. The former problem ishandled in the MM4230KP/MM5230KP by exploitingthe inherent redundancy of the bail code(see Table 2). The latter inconsistency is resolvedby making arbitrary equivalences between theunique characters. The two tables show the treatmentof both the characters wh ich have equivalentsin both codes, and those characters, and the functions,which do not. Encoding and decoding theSelectric functions that the user requires is amatter of conventional Boolean logic. A typicalexample is shown below.For electrical, environmental and mechanical details,refer to the MM4230/MM5230 data sheet.typical applicationBAilCODEINPUTSfROMSELECTRICASCII(lUTPIJTCOWlRlIEI~ INPUT,,,:=11" ,lis,-f--A HIGH ASCII I. $,1.",,, O"'~"tA lOW S.I«t"c to ASCII Inp"1I,r-+:1'