Peripheral Interface Adaptor
The PIA chip is an off-the-shelf 6532 Peripheral Interface Adaptor which has three functions: a programmable timer, 128 bytes of RAM, and two 8 bit parallel I/O ports.
Grouped
The PIA functions are best examined in the following sections, which show how to use them.
IO Ports
Timers
RAM
Registers
For details on individual registers, click on the register name in the following table.
| Name | Purpose | |
| $280 | SWCHA | Port A; input or output (read or write) Used for controllers (joystick, paddles, etc.) |
| $281 | SWACNT | Port A data direction register, 0= input, 1=output |
| $282 | SWCHB | Port B; console switches (read only) |
| $283 | SWBCNT | Port B data direction register (hardwired as input) |
| $284 | INTIM | Timer output (read only) |
| $294 | TIM1T | set 1 clock interval (838 nanosecond/interval) |
| $295 | TIM8T | set 8 clock interval (6.7 microsecond/interval) |
| $296 | TIM64T | set 64 clock interval (53.6 microsecond/interval) |
| $297 | T1024T | set 1024 clock interval (858.2 microsecond/interval) |
Notes
- one clock is also one microprocessor machine cycle
Function
| Timers | Interval Timers | |
| RAM | ||
| IO Ports | ||