TDA8029 Datasheet, PDF (15/59 Pages) NXP Semiconductors – Low power single card reader

Philips Semiconductors
TDA8029
Low power single card reader
The baud rates in modes 1 and 3 are determined by the overflow rate of timer 2, given by
Equation 1:
Baud rate = ^T----ⁱ--^m-----^e---^r-----²-----^o---^v1---^e6---^r---^f--^l--^o---^w-------^r--^a----^t--^e-
(1)
The timer can be configured for either timer or counter operation. In many applications, it
is configured for timer operation (C/T2 = 0). Timer operation is different for timer 2 when it
is being used as a baud rate generator.
Usually, as a timer it would increment every machine cycle (i.e. ¹â„₁₂ f_osc). As a baud rate
generator, it increments every state time (i.e. ¹â„₂f_osc). Thus the modes 1 and 3 baud rate
formula is as Equation 2:
Baud rate = ₃----₂----_×-----_[--₆---₅-^O--₅---^s3--^c-₆--ⁱ--^l-_–-^l--^a-₍---^tR--^o--_C-^r---_A---^f-_P-^r--^e-₂--^q--_H--^u--_,-^e--_R-ⁿ----_Cc---^y-_A----_P----₂---_L----₎---_]
(2)
Where (RCAP2H, RCAP2L) is the contents of RCAP2H and RCAP2L registers taken as a
16-bit unsigned integer.
The timer 2 as a baud rate generator is valid only if RCLK = 1 and/or TCLK = 1 in the
T2CON register. Note that a rollover in TH2 does not set TF2, and will not generate an
interrupt. Thus, the timer 2 interrupt does not have to be disabled when timer 2 is in the
baud rate generator mode. Also if the EXEN2 (T2 external enable) flag is set, a HIGH to
LOW transition on T2EX (timer/counter 2 trigger input) will set the EXF2 (T2 external) flag
but will not cause a reload from (RCAP2H and RCAP2L) to (TH2 and TL2). Therefore,
when timer 2 is used as a baud rate generator, T2EX can be used as an additional
external interrupt, if needed.
When timer 2 is in the baud rate generator mode, never try to read or write TH2 and TL2.
As a baud rate generator, timer 2 is incremented every state time (¹â„₂f_osc) or
asynchronously from controller I/O T2; under these conditions, a read or write of TH2 or
TL2 may not be accurate. The RCAP2 registers may be read, but should not be written to,
because a write might overlap a reload and cause write and/or reload errors. The timer
should be turned off (clear TR2) before accessing the timer 2 or RCAP2 registers. See
Figure 5 for an overview.
Table 12: Timer 2 generated commonly used baud rates
Baud rate (Bd)
Crystal oscillator
frequency (MHz)
Timer
RCAP2H (hex)
375k
12
FF
9.6k
12
FF
2.8k
12
FF
2.4k
12
FF
1.2k
12
FE
300
12
FB
110
12
F2
300
6
FD
110
6
F9
RCAP2L (hex)
FF
D9
B2
64
C8
1E
AF
8F
57
9397 750 14145
Product data sheet
Rev. 03 — 22 February 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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