rf2051 RF Micro Devices, rf2051 Datasheet - Page 17

• Manufacturer Part Number: rf2051
• Description: High Performance Wideband Rf Synthesizer/vco With Integrated Rf Mixers
• Manufacturer: RF Micro Devices

Write
Initially ENX is high and SDATA is high impedance. The write operation begins with the controller starting SCLK. On the first fall-
ing edge of SCLK the baseband asserts ENX low. The second rising edge of SCLK is reserved to allow the SDI to initialize, and
the third rising edge is used to define whether the operation will be a write or a read operation. In write mode the baseband will
drive SDATA for the entire telegram. RF2051 will read the data bit on the rising edge of SCLK.
The next 7 data bits are the register address, MSB first. This is followed by the payload of 16 data bits for a total write mode
transfer of 24 bits. Data is latched into RF2051 on the last rising edge of SCLK (after ENX is asserted high).
For more information, please refer to the timing diagram on page 16.
The maximum clock speed for a register write is 19.2MHz. A register write therefore takes approximately 1.3us. The data is
latched on the rising edge of the clock. The datagram consists of a single start bit followed by a ‘0’ (to indicate a write opera-
tion). This is then followed by a seven bit address and a sixteen bit data word.
Note that since the serial bus does not require the presence of the crystal clock, it is necessary to insert an additional rising
clock edge before the ENX line is set low to ensure the address/data are read correctly.
Read
Initially ENX is high and SDATA is high impedance. The read operation begins with the controller starting SCLK. The controller is
in control of the SDATA line during the address write operation. On the first falling edge of SCLK the baseband asserts ENX low.
The second rising edge of SCLK is reserved to allow the SDI to initialize, and the third rising edge is used to define whether the
operation will be a write or a read operation. In read mode the baseband will drive SDATA for the address portion of the tele-
gram, and then control will be handed over to RF2051 for the data portion. RF2051 will read the data bits of the address on
the rising edge of SCLK. After the address has been written, control of the SDATA line is handed over to RF2051. One and a half
clocks are reserved for turn-around, and then the data bits are presented by RF2051. The data is set up on the rising edge of
SCLK, and the controller latches the data on the falling edge of SCLK. At the end of the data transmission, RF2051 will release
control of the SDATA line, and the controller asserts ENX high. The SDATA port on RF2051 transitions from high impedance to
low impedance on the first rising edge of the data portion of the transaction (for example, 3 rising edges after the last address
bit has been read), so the controller chip should be presenting a high impedance by that time.
For more information, please refer to the timing diagram on page 16.
The maximum clock speed for a register read is 19.2MHz. A register read therefore takes approximately 1.4us. The address is
latched on the rising edge of the clock and the data output on the falling edge. The datagram consists of a single start bit fol-
lowed by a ‘1’ (to indicate a read operation), followed by a seven bit address. A 1.5 bit delay is introduced before the sixteen bit
data word representing the register content is presented to the receiver.
Note that since the serial bus does not require the presence of the crystal clock, it is necessary to insert an additional rising
clock edge before the ENX line is set low to ensure the address is read correctly.
Rev A1 DS090106
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RF2051
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