TDA8029 Philips Semiconductors, TDA8029 Datasheet - Page 14

• Manufacturer Part Number: TDA8029
• Description: Low power single card reader
• Manufacturer: Philips Semiconductors

Philips Semiconductors
8.2.2
Table 7 Timer/counter 2 mode control register bits
Table 8 Description of register bits
Note
1. Do not write logic 1s to reserved bits. These bits may be used in future 80C51 family products to invoke new features.
8.2.3
In the 16-bit auto-reload mode, timer 2 can be configured
as either a timer or counter (bit C/T2 in register T2CON)
and programmed to count up or down. The counting
direction is determined by bit DCEN (down-counter
enable) which is located in the T2MOD register. When
reset, DCEN = 0 and timer 2 will default to counting up. If
DCEN = 1, timer 2 can count up or down depending on the
value of T2EX.
When DCEN = 0, timer 2 will count up automatically.
In this mode there are two options selected by bit EXEN2
in register T2CON. If EXEN2 = 0, then timer 2 counts up to
0FFFFh and sets the TF2 overflow flag upon overflow.
This causes the timer 2 registers to be reloaded with the
16-bit value in RCAP2L and RCAP2H. The values in
RCAP2L and RCAP2H are preset by software. If
EXEN2 = 1, then a 16-bit reload can be triggered either by
an overflow or by a HIGH to LOW transition at controller
input T2EX. This transition also sets the EXF2 bit. The
timer 2 interrupt, if enabled, can be generated when either
TF2 or EXF2 are logic 1. See Fig.3 for an overview.
2003 Oct 30
Symbol
7 to 2
1
0
Low power single card reader
In that case, the reset or inactive value of the new bit will be logic 0, and its active value will be logic 1. The value
read from a reserved bit is indeterminate.
BIT
BIT
T
A
IMER
UTO
-
T2OE
DCEN
/
RELOAD MODE
COUNTER
SYMBOL
7
2 M
ODE CONTROL REGISTER
(
Not implemented. Reserved for future use; note 1.
Timer 2 Output Enable.
Down Counter Enable. When set, allows timer 2 to be configured as up-/down-counter.
UP
-
OR DOWN
6
-
COUNTER
5
)
(T2MOD)
14
4
DCEN = 1 enables timer 2 to count up- or down. This
mode allows T2EX to control the direction of count. When
a HIGH level is applied at T2EX timer 2 will count up.
Timer 2 will overflow at 0FFFFh and set the TF2 flag,
which can then generate an interrupt, if the interrupt is
enabled. This timer overflow also causes the 16-bit value
in RCAP2L and RCAP2H to be reloaded into the timer
registers TL2 and TH2. When a LOW level is applied at
T2EX this causes timer 2 to count down. The timer will
underflow when TL2 and TH2 become equal to the value
stored in RCAP2L and RCAP2H. Timer 2 underflow sets
the TF2 overflow flag and causes 0FFFFh to be reloaded
into the timer registers TL2 and TH2. See Fig.4 for an
overview.
The external flag EXF2 toggles when timer 2 underflows or
overflows. This EXF2 bit can be used as a 17th bit of
resolution if needed. The EXF2 flag does not generate an
interrupt in this mode of operation.
DESCRIPTION
3
2
T2OE
Product specification
1
TDA8029
DCEN
0