Rainbow Electronics ATtiny12 - Manual (Page 13)

13
ATtiny11/12
1006C–09/01
EEPROM Data Memory The ATtiny12 contains 64 bytes of data EEPROM memory. It is organized as a separate
data space, in which single bytes can be read and written. The EEPROM has an endur-
ance of at least 100,000 write/erase cycles. The access between the EEPROM and the
CPU is described on page 36, specifying the EEPROM Address Register, the EEPROM
Data Register, and the EEPROM Control Register.
For SPI data downloading, see “Memory Programming” on page 44 for a detailed
description.
Memory Access and
Instruction Execution
Timing This section describes the general access timing concepts for instruction execution and
internal memory access.
The AVR CPU is driven by the System Clock Ø, directly generated from the external
clock crystal for the chip. No internal clock division is used.
Figure 14 shows the parallel instruction fetches and instruction executions enabled by
the Harvard architecture and the fast-access register file concept. This is the basic pipe-
lining concept to obtain up to 1 MIPS per MHz with the corresponding unique results for
functions per cost, functions per clocks, and functions per power-unit.
Figure 14. The Parallel Instruction Fetches and Instruction Executions
Figure 15 shows the internal timing concept for the register file. In a single clock cycle,
an ALU operation using two register operands is executed and the result is stored back
to the destination register.
Figure 15. Single-cycle ALU Operation
System Clock Ø
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
T1 T2 T3 T4
System Clock Ø
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
T1 T2 T3 T4