Disclaimer Typical values contained in this data sheet are based on simulations and characterization of actual ATtiny88 AVR? microcontrollers manufactured on the typical process technology. Applicable automotive min. and max. values are based on characterization of devices representative of the whole process excursion （corner run）

　　Port A （PA3:0） Port A is a 4-bit bi-directional I/O port with internal pull-up resistors （selected for each bit） in 32-lead TQFP and 32-pad QFN package. The PA3..0 output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs， port A pins that are externally pulled low will source current if the pull-up resistors are activated. The port A pins are tri-stated when a reset condition becomes active， even if the clock is not running. 1.2.4 Port B （PB7:0） Port B is an 8-bit bi-directional I/O port with internal pull-up resistors （selected for each bit）。 The port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs， Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The port B pins are tri-stated when a reset condition becomes active， even if the clock is not running. Depending on the clock selection fuse settings， PB6 can be used as input to the internal clock operating circuit. The various special features of port B are elaborated in Section 10.3.2 “Alternate Functions of Port B” on page 59 and Section 6. “System Clock and Clock Options” on page 25.