ata5277-pcq ATMEL Corporation, ata5277-pcq Datasheet - Page 7

• Manufacturer Part Number: ata5277-pcq
• Description: Stand-alone Antenna Driver
• Manufacturer: ATMEL Corporation

Figure 8. Control/Status Command Structure
4669B–RKE–10/03
DIO
Command Mode
Standby or
Wake-up
Start
CMD0
IN
Any command is preceded by a start bit. Note again that, if the ATA5277 is woken up by
one of the external switches, the wake-up signal from the ATA5277 (slave) to the micro-
controller (master) on the DIO-line is already the start bit of the first command.
It is followed by the command bits CMD0...CMD3. Bits CMD0 to CMD2 are used to
select one of the eight registers of control and status bits. These registers have a depth
of four bits and are used to configure the ATA5277 and to check its status. The CMD3
bit is used to select the operation mode of the ATA5277 after the current command has
been processed (i.e., switch to modulation mode or stay in command mode).
The next four bits of the protocol (Bit0 to Bit3) are the data bits. Depending on the
selected register, these bits are to be transmitted by the microcontroller (for control com-
mands) or by ATA5277 (for status commands). Note that even if data is transmitted by
ATA5277, the initial falling edge for any bit has to be transmitted by the microcontroller,
as it is the master of the transmission.
Furthermore, the IC has a built-in bit error check for input bits. If no errors are detected
during a command transfer, the IC acknowledges the command with N_ACKN = 0. If a
bit error is detected, the transfer is not acknowledged (N_ACKN =1), the received data
is dismissed and the command has to be sent again immediately.
Figure 7. Data Consistency Check
As can be seen in Figure 7, the state of the DIO line is sampled twice during the data-
valid time. During this time, the state must not change, both samples must result in the
same value. If they differ, the N_ACKN bit is set to '1' and thus a fault is reported at the
end of the sequence. The bit is reset after each control/status command (i.e., after it is
transmitted to the microcontroller).
If the controller receives a ’1’ acknowledge bit, it has to repeat the command immedi-
ately (i.e., without transmitting the stop bit), starting again with the start bit.
The stop bit is used to end the command mode. After receiving the stop bit, the IC
switches to modulation mode. Note that this bit is omitted if the CMD3 bit has been sent
as a '1' (i.e., another command is to be transmitted).
CMD1
Command Bits
IN
CMD2
IN
CMD3
IN
IN/OUT
Bit 0
Control and Status Bits
IN/OUT
Bit 1
IN/OUT
ATA5277 [Preliminary]
Bit 2
IN/OUT
Bit 3
N_Ackn
OUT
Stop
Modulation
Mode
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