Rainbow Electronics RA01 - Manual (Page 9)

RA01
Version: 1.0 Date: 10/8/2008
Note 1: See matching circuit parameters and antenna design guide for information, and Application Notes available
from http://www.hoperf.com.
Note 2: Using other than a 10 MHz crystal is not recommended because the crystal referred timing and frequency
parameters will change accordingly.
Note 3: During this period, commands are not accepted by the chip.
Note 4: Autocalibration can be turned off.
CONTROL INTERFACE
Commands to the receiver are sent serially. Data bits on pad SDI are shifted into the device upon the rising edge of the
clock on pad SCK whenever the chip select pad nSEL is low. When the nSEL signal is high, it initializes the serial interface.
The number of bits sent is an integer multiple of 8. All commands consist of a command code, followed by a varying
number of parameter or data bits. All data are sent MSB first (e.g. bit 15 for a 16-bit command). Bits having no influence
(don’t care) are indicated with X. The Power On Reset (POR) circuit sets default values in all control registers.
The receiver will generate an interrupt request (IRQ) for the microcontroller on the following events:
• Supply voltage below the preprogrammed value is detected (LBD)
• Wake-up timer timeout (WK-UP)
• FIFO received the preprogrammed amount of bits (FFIT)
• FIFO overflow (FFOV)
FFIT and FFOV are applicable only when the FIFO is enabled. To find out why the nIRQ was issued, the status bits should
be read out.
Timing Specification
Symbol Parameter Minimum value [ns]
t
CH
Clock high time 25
t
CL
Clock low time 25
t
SS
Select setup time (nSEL falling edge to SCK rising edge) 10
t
SH
Select hold time (SCK falling edge to nSEL rising edge) 10
t
SHI
Select high time 25
t
DS
Data setup time (SDI transition to SCK rising edge) 5
t
DH
Data hold time (SCK rising edge to SDI transition) 5
t
OD
Data delay time 10
Timing Diagram
BIT15 BIT14 BIT13 BIT8 BIT7 BIT1 BIT0
BIT15 BIT14 BIT13 BIT8 BIT7 BIT1 BIT0
tDS
tOD tCH tCL tSH
tSHI
tSS
tDH
nSEL
SCK
SDI
SDO
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