4283 Group
TIMERS
The 4283 Group has the programmable timer.
• Programmable timer
The programmable timer has a reload register and enables
the frequency dividing ratio to be set. It is decremented from a
setting value n. When it underflows (count to n + 1), a timer 1
underflow flag is set to “1,” new data is loaded from the reload
register, and count continues (auto-reload function).
FF16
n: Counter initial value
Count starts
Reload
Reload
n
1st underflow
2nd underflow
0016
Time
n+1 count
n+1 count
“1”
“0”
Timer 1 underflow flag
A skip instruction is executed
Fig. 12 Auto-reload function
The 4283 Group timer consists of the following circuit.
• Timer 1 : 8-bit programmable timer
• Timer 2 : 8-bit programmable timer
These timers can be controlled with the timer control registers
V1 and V2.
Each timer function is described below.
Table 3 Function related timer
Control
Frequency
dividing ratio
1 to 256
Circuit
Timer 1
Use of output signal
Structure
Count source
• Carrier wave output (CARRY)
register
V1
• Carrier wave output control
8-bit programmable
binary down counter • Bit 5 of watchdog timer
8-bit programmable • f(XIN)
V2
Timer 2
1 to 256
16384
• Carrier wave output
binary down counter • f(XIN)/2
14-bit timer
• Watchdog timer
14-bit fixed frequency • Instruction clock
• Timer 1 count source
Rev.1.01 Mar 20, 2006 page 11 of 62
REJ03B0109-0101
RENESAS [ RENESAS TECHNOLOGY CORP ]
