Memory

Input/Output Programming

2.3.3 RAM

The user RAM consists of 352 bytes of a shared stack area. The RAM starts at address $0020 and ends at address $017F. The stack begins at address $00FF. The stack pointer can access 64 bytes of RAM in the range $00FF to $00C0.

NOTE: Using the stack area for data storage or temporary work locations requires care to prevent it from being overwritten due to stacking from an interrupt or subroutine call.

2.4 Input/Output Programming

In user mode, 20 lines (28-pin PDIP or 28-pin SOIC) or 24 lines (44-lead PLCC) are arranged as three 8-bit I/O ports. These ports are programmable as either inputs or outputs under software control of the data direction registers. For detailed information, refer to Section 7. Parallel Input/Output (I/O).

MC68HC05RC16 — Rev. 3.0

 

General Release Specification

 

 

 

MOTOROLA

Memory

31