UPSD3354DV-40U6 Datasheet, PDF (97/272 Pages) STMicroelectronics – fast 8032 MCU with programmable logic

UPSD33xx
Standard 8032 timer/counters
20.5.4
Mode 3
Timer 1 in mode 3 simply holds its count. The effect is the same as setting TR1 = 0.
Timer 0 in mode 3 establishes TL0 and TH0 as two separate counters. The logic for mode 3
on Timer 0 is shown in Figure 23 on page 99. TL0 uses the Timer 0 control Bits: C/T, GATE,
TR0, and TF0, as well as the pin EXTINT0. TH0 is locked into a timer function (counting at a
rate of 1/12 f_OSC) and takes over the use of TR1 and TF1 from Timer 1. Thus, TH0 now
controls the “Timer 1“ interrupt flag.
Mode 3 is provided for applications requiring an extra 8-bit timer on the counter (see
Figure 23 on page 99). With Timer 0 in mode 3, a UPSD33xx device can look like it has
three Timer/Counters (not including the PCA). When Timer 0 is in mode 3, Timer 1 can be
turned on and off by switching it out of and into its own mode 3, or can still be used by the
serial port as a baud rate generator, or in fact, in any application not requiring an interrupt.
Table 56. TMOD: Timer Mode register (SFR 89h, reset value 00h)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
GATE
C/T
M[1:0]
GATE
C/T
M[1:0]
ct(s) Table 57.
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TMOD register bit definition
Symbol
R/W
Timer
Definition (T/C is abbreviation for
timer/counter)
GATE
R,W
Gate control.
When GATE = 1, T/C is enabled only while pin
EXTINT1 is '1' and the flag TR1 is '1.' When GATE
= 0, T/C is enabled whenever the flag TR1 is '1.'
C/T
M[1:0]
Counter or Timer function select.
R,W
When C/T = 0, function is timer, clocked by
internal clock. C/T = 1, function is counter, clocked
by signal sampled on external pin, C1.
Timer 1
Mode Select.
00b = 13-bit T/C. 8 bits in TH1 with TL1 as 5-bit
pre-scaler.
R,W
01b = 16-bit T/C. TH1 and TL1 are cascaded. No
pre-scaler.
10b = 8-bit auto-reload T/C. TH1 holds a constant
and loads into TL1 upon overflow.
11b = Timer Counter 1 is stopped.
Doc ID 9685 Rev 7
97/272