PIC17C75X Datasheet, PDF (185/320 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers

PIC17C75X
18.2 Q Cycle Activity
Each instruction cycle (Tcy) is comprised of four Q
cycles (Q1-Q4). The Q cycle is the same as the device
oscillator cycle (TOSC). The Q cycles provide the tim-
ing/designation for the Decode, Read, Process Data,
Write etc., of each instruction cycle. The following dia-
gram shows the relationship of the Q cycles to the
instruction cycle.
The four Q cycles that make up an instruction cycle
(Tcy) can be generalized as:
Q1: Instruction Decode Cycle or forced No
operation
Q2: Instruction Read Cycle or No operation
Q3: Process the Data
Q4: Instruction Write Cycle or No operation
Each instruction will show the detailed Q cycle opera-
tion for the instruction.
FIGURE 18-2: Q CYCLE ACTIVITY
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Tosc
Tcy1
Tcy2
Tcy3
© 1997 Microchip Technology Inc.
DS30264A-page 185