1 - Al Kossow's Bitsavers

TMS49648192·WORD BY 8·BIT READ·ONLY MEMORYdata out (Q1-Q8)The eight outputs must be enabled by both pins 20 and 21 before the output word can be read. Data will remainvalid until the address is changed or the outputs are disabled (chip deselected). When disabled, the three-state outputsare in a high-impedance state. 01 is considered the least-significant bit, 08 the most-significant bit.The outputs will drive two Series 54/74 TTL circuits without external components.page operationThe ROM is organized into 8K x 8-bit bytes. Only 12 address bits or a maximum of 4K bytes may be accessed atone time. The 4K address space is segmented into four 1 K banks and memory is partitioned into eight 1 K pages.Bank 3 containing page 7 is always resident. Any three of the eight pages, 0 thru 7, are immediately accessable.The banks, which are defined by page pointers, are selected by address bits A3 and A4 (see Table 1).TABLE 1A4 A3 BANK ADDRESS RANGEL L 0 000 - 3FFL H 1 400 - 7FFH L 2 BOO - BFFResident 3 COO - FDF:llo3:oCD