AT&T 3B2/300 Technical Reference Manual page 447

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
ID/Vector Register
The GPSC card ID /Vector Register is a 16-bit register that is used for two functions. Initially the
register contains the 16-bit GPSC card ID code. The GPSC card ID code is Ox 0104. Later the register
contains an 8-bit interrupt vector for the ID code. The interrupt vector is returned in response to an
Interrupt Acknowledge (PIAK[O]) signal.
Page Register
The GPSC card uses a 24-bit address to do main memory operations. The lower 17 bits are
provided by the 80C186 Microprocessor. The most significant 7 bits are provided by the Page Register.
The Page Register is a write only register for the 80C186 Microprocessor. The two most significant
address bits (bits 06 and 05) of the Page Register are always zero. This allows the Page Register to
select thirty-two 128 kilobyte segments of main memory. The Page Register is addressed by the 80186
Microprocessor at its I/0 address Ox 0482.
3-194 TECHNICAL REFERENCE MANUAL