ADE7566ASTZF8-RL2 AD [Analog Devices], ADE7566ASTZF8-RL2 Datasheet - Page 116

• Manufacturer Part Number: ADE7566ASTZF8-RL2
• Description: Single-Phase Energy Measurement IC with 8052 MCU, RTC, and LCD Driver
• Manufacturer: AD [Analog Devices]

ADE7566/ADE7569
To transmit, the 8 data bits must be written into the Serial Port
Buffer SFR (SBUF, 0x99). The ninth bit must be written to TB8
in the Serial Communications Control Register Bit Description
SFR (SCON, 0x98). When transmission is initiated, the 8 data
bits from SBUF are loaded into the transmit shift register (LSB
first). The ninth data bit, held in TB8, is loaded into the ninth
bit position of the transmit shift register. The transmission
starts at the next valid baud rate clock. The transmit interrupt
flag (TI) is set as soon as the transmission completes, when the
stop bit appears on TxD.
All of the following conditions must be met at the time the final
shift pulse is generated to receive a character:
•
•
If any of these conditions are not met, the received frame is
irretrievably lost, and the receive interrupt flag (RI) is not set.
Reception for Mode 2 is similar to that of Mode 1. The 8 data
bytes are input at RxD (LSB first) and loaded onto the receive
shift register. If the received frame has met the previous criteria,
the following events occur:
•
•
•
Mode 3 (9-Bit UART with Variable Baud Rate)
Mode 3 is selected by setting both SM0 and SM1. In this mode,
the 8051 UART serial port operates in 9-bit mode with a variable
baud rate. The baud rate is set by a timer overflow rate. Timer 1
or Timer 2 can be used to generate baud rates, or both timers
can be used simultaneously where one generates the transmit
rate and the other generates the receive rate. There is also a
dedicated timer for baud rate generation, the UART timer,
which has a fractional divisor to precisely generate any baud
rate (see the UART Timer Generated Baud Rates section). The
operation of the 9-bit UART is the same as for Mode 2, but the
baud rate can be varied.
In all four modes, transmission is initiated by any instruction
that uses SBUF as a destination register. Reception is initiated in
Mode 0 when RI = 0 and REN = 1. Reception is initiated in the
other modes by the incoming start bit if REN = 1.
If the extended UART is disabled (EXTEN = 0 in the CFG
SFR), RI must be 0 to receive a character. This ensures that
the data in SBUF is not overwritten if the last received
character has not been read.
If multiprocessor communication is enabled by setting
SM2, the received ninth bit must be set to receive a character.
This ensures that only frames with the ninth bit set, frames
that contain addresses, generate a receive interrupt.
The 8 bits in the receive shift register are latched into the
SBUF SFR.
The ninth data bit is latched into RB8 in the SCON SFR.
The receiver interrupt flag (RI) is set.
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UART BAUD RATE GENERATION
Mode 0 Baud Rate Generation
The baud rate in Mode 0 is fixed.
Mode 2 Baud Rate Generation
The baud rate in Mode 2 depends on the value of the PCON.7
(SMOD) bit in the Program Control SFR (PCON, 0x87). If
SMOD = 0, the baud rate is 1/32 of the core clock. If SMOD = 1,
the baud rate is 1/16 of the core clock.
Mode 1 and Mode 3 Baud Rate Generation
The baud rates in Mode 1 and Mode 3 are determined by the
overflow rate of the timer generating the baud rate, that is,
either Timer 1, Timer 2, or the dedicated baud rate generator,
UART timer, which has an integer and fractional divisor.
Timer 1 Generated Baud Rates
When Timer 1 is used as the baud rate generator, the baud rates
in Mode 1 and Mode 3 are determined by the Timer 1 overflow
rate. The value of SMOD is as follows:
The Timer 1 interrupt should be disabled in this application.
The timer itself can be configured for either timer or counter
operation, and in any of its three running modes. In the most
typical application, it is configured for timer operation in
autoreload mode (high nibble of TMOD = 0010 binary). In that
case, the baud rate is given by the following formula:
Timer 2 Generated Baud Rates
Baud rates can also be generated by using Timer 2. Using Timer 2
is similar to using Timer 1 in that the timer must overflow 16 times
before a bit is transmitted or received. Because Timer 2 has a
16-bit autoreload mode, a wider range of baud rates is possible.
Therefore, when Timer 2 is used to generate baud rates, the
timer increments every two clock cycles rather than every core
machine cycle as before. It increments six times faster than
Timer 1, and, therefore, baud rates six times faster are possible.
Because Timer 2 has 16-bit autoreload capability, very low baud
rates are still possible.
Mode 2 Baud Rate =
Mode 1 and Mode 3 Baud Rate =
Mode 1 and Mode 3 Baud Rate =
Mode 1 and Mode 3 Baud Rate =
Mode 0 Bau
2
SMOD
32
×
Timer 1 Overflow Rate
d Rate
Preliminary Technical Data
=
⎛
⎜
⎝
2
SMOD
f
12
32
core
⎞
⎟
⎠
× f
16
CORE
1
2
SMOD
32
× Timer 2 Overflow Rate
×
(
256
f
−
core
TH1
)