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3.7
8-Bit Timers (TMRA)
The TMP91C824 features 4 channel (TMRA0 to TMRA3) built-in 8-bit timers.
These timers are paired into 2 modules: TMRA01 and TMRA23. Each module consists of 2
channels and can operate in any of the following 4 operating modes.
•
8-bit interval timer mode
•
16-bit interval timer mode
•
8-bit programmable square wave pulse generation output mode (PPG: Variable duty cycle
with variable period)
•
8-bit pulse width modulation output mode (PWM: Variable duty cycle with constant
period)
Figure 3.7.1 to Figure 3.7.2 show block diagrams for TMRA01 and TMRA23.
Each channel consists of an 8-bit up counter, an 8-bit comparator and an 8-bit timer register.
In addition, a timer flip-flop and a prescaler are provided for each pair of channels.
The operation mode and timer flip-flop condition are controlled by 5-byte registers.
We call control registers SFRs: Special function registers.
Each of the two modules (TMRA01 and TMRA23) can be operated independently. All
modules operate in the same manner; hence only the operation of TMRA01 is explained here.
The contents of this chapter are as follows.
3.7.1 Block Diagrams
3.7.2 Operation of Each Circuit
3.7.3 SFRs
3.7.4 Operation in Each Mode
(1) 8-bit timer mode
(2) 16-bit timer mode
(3) 8-bit PPG (Programmable pulse generation) output mode
(4) 8-bit PWM (Pulse width modulation) output mode
(5) Settings for each mode
External pin
SFR
(Address)
Table 3.7.1 Registers and Pins for Each Module
Module
Input pin for external clock
Output pin for timer flip-flop
Timer run register
Timer register
Timer mode register
Timer flip-flop control register
91C824-90
TMRA01
TMRA23
TA0IN
None
(shared with PB0)
TA1OUT
TA3OUT
(shared with PB1)
(shared with PB2)
TA01RUN (0100H)
TA23RUN (0108H)
TA0REG (0102H)
TA2REG (010AH)
TA1REG (0103H)
TA3REG (010BH)
TA01MOD (0104H)
TA23MOD (010CH)
TA1FFCR (0105H)
TA3FFCR (010DH)
TMP91C824
2008-02-20
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