High-Performance SAB 80C517A/83C517A-5 8-Bit CMOS Single ...

SAB 80C517A/83C517A-5Pin Definitions and Functions (cont’d)Symbol Pin Number I/O *) FunctionXTAL2 39 12 – XTAL2Input to the inverting oscillator amplifier andinput to the internal clock generator circuits.XTAL1 40 13 – XTAL1Output of the inverting oscillator amplifier.To drive the device from an external clocksource, XTAL2 should be driven, whileXTAL1 is left unconnected. There are norequirements on the duty cycle of theexternal clock signal, since the input to theinternal clocking circuitry is devided downby a divide-by-two flip-flop. Minimum andmaximum high and low times as well asrise/fall times specified in the ACcharacteristics must be observed.P2.0 - P2.7 41 - 48 14 - 21 I/O Port 2is a bidirectional I/O port with internal pullupresistors. Port 2 pins that have 1 swritten to them are pulled high by theinternal pull-up resistors, and in that statecan be used as in-puts. As inputs, port 2pins being externally pulled low will sourcecurrent (I IL , in the DC characteristics)because of the internal pull-up resistors.Port 2 emits the high-order address byteduring fetches from external programmemory and during accesses to externaldata memory that use 16-bit addresses(MOVX @DPTR). In this application it usesstrong internal pull-up resistors whenissuing1 s. During accesses to externaldata memory that use 8-bit addresses(MOVX @Ri), port 2 issues the contents ofthe P2 special function register.* I = InputO = OutputP-LCC-84P-MQFP-100-2Semiconductor Group 11