ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 117

• Manufacturer Part Number: ade7566
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

Timer 2 is selected as the baud rate generator by setting TCLK
and/or RCLK in Timer/Counter 2 Control SFR (T2CON, 0xC8).
The baud rates for transmit and receive can be simultaneously
different. Setting RCLK and/or TCLK puts Timer 2 into its baud
rate generator mode as shown in Figure 100.
In this case, the baud rate is given by the following formula:
UART Timer Generated Baud Rates
The high integer dividers in a UART block mean that high speed
baud rates are not always possible. In addition, generating baud
rates requires the exclusive use of a timer, rendering it unusable
for other applications when the UART is required. To address
this problem, each ADE7566/ADE7569 has a dedicated baud
rate timer (UART timer) specifically for generating highly
accurate baud rates. The UART timer can be used instead of
Timer 1 or Timer 2 for generating very accurate high speed
UART baud rates, including 115,200 bps. This timer also allows
a much wider range of baud rates to be obtained. In fact, every
desired bit rate from 12 bps to 393,216 bps can be generated to
within an error of ±0.8%. The UART timer also frees up the other
three timers, allowing them to be used for different applications.
A block diagram of the UART timer is shown in Figure 99.
Mode 1 and Mode 3 Baud Rate =
(
16
×
[
65536
TRANSITION
−
T2EX
DETECTOR
PIN
PIN
(
f
T2
RCAP
NOTE: AVAILABILITY OF ADDITIONAL
EXTERNAL INTERRUPT
CORE
f
CORE
2
H
:
RCAP
C/ T2 = 0
C/ T2 = 1
2
L
)
]
EXEN2
)
CONTROL
CONTROL
TR2
Figure 100. Timer 2, UART Baud Rates
EXF 2
Rev. 0 | Page 117 of 136
RCAP2L
(8 BITS)
TL2
TIMER 2
INTERRUPT
RCAP2H
(8 BITS)
TH2
Two SFRs, Enhanced Serial Baud Rate Control SFR (SBAUDT,
0x9E) and UART Timer Fractional Divider SFR (SBAUDF,
0x9D), are used to control the UART timer. SBAUDT is the
baud rate control SFR; it sets up the integer divider (DIV) and
the extended divider (SBTH) for the UART timer.
The appropriate value to write to the DIV[2:0] and SBTH[1:0]
bits can be calculated using the following formula where f
defined in the POWCON SFR (see Table 25). Note that the DIV
value must be rounded down to the nearest integer.
FRACTIONAL
DIVIDER
RELOAD
OVERFLOW
DIV
TIMER 2
+
SBTH
÷(1 + SBAUDF/64)
÷2
Figure 99. UART Timer, UART Baud Rate
f
DIV + SBTH
÷32
CORE
1
1
=
OVERFLOW
2
log
TIMER 1
0
0
0
UART TIMER
Rx/Tx CLOCK
⎛
⎜
⎜
⎝
16
1
×
log
Rx CLOCK
TIMER 1/TIMER 2
RCLK
TCLK
Baud
f
16
16
CORE
( )
2
1
1
SMOD
ADE7566/ADE7569
Rate
Tx CLOCK
0
0
TIMER 1/TIMER 2
Rx
CLOCK
Tx
CLOCK
⎞
⎟
⎟
⎠
UARTBAUDEN
Rx CLOCK
Tx CLOCK
CORE
is