CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
5 Software Programming
5.1 C-BUS Serial Interface
C-BUS is the serial interface used by a µC to transfer data, control, and status information, to and from the
internal registers of the chip. Every transaction consists of one address byte that may be followed by one or
two bytes of data.
Data sent from the µC to the chip on the CMD DATA line is clocked in on the rising edge of SERIAL CLOCK.
RPLY DATA sent from the chip to the µC is valid when SERIAL CLOCK is high. See Figure 22. This serial
interface is compatible with most common µC serial interfaces such as SCI, SPI, and Microwire.
a) Single byte from µC
CS
SERIAL CLOCK
CMD DATA
RPLY DATA
76543 2 10
Address (01 Hex = Reset)
Hi-Z
Note:
The SERIAL CLOCK line may be high
or low at the start and end of each
transaction.
= Level not important
b) One Address and 2 Data bytes from µC
CS
SERIAL CLOCK
CMD DATA
RPLY DATA
765432 10
Address
Hi-Z
765432 10
Data to Chip
765432 10
Data to Chip
c) One Address byte from µC and 2 Reply bytes from the Chip
CS
SERIAL CLOCK
CMD DATA
RPLY DATA
765432 10
Address
Hi-Z
765432 10
Data from Chip
765432 10
Data from Chip
Figure 22: C-BUS transaction timing diagram.
2003 CML Microsystems Plc
28
D/838/8
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