CMX624 CML Microcircuits, CMX624 Datasheet - Page 13

• Manufacturer Part Number: CMX624
• Description: V.23-Bell 202 Modem
• Manufacturer: CML Microcircuits

V23 / Bell 202 Modem
CMX624
1.5.11 ‘C-BUS’ Interface
This block provides for the transfer of data and control or status information between the CMX624’s internal
registers and the µC over the ‘C-BUS’ serial bus. Each transaction, see Figure 7, consists of a single Register
Address byte sent from the µC which may be followed by a single data byte sent from the µC to be written into
one of the CMX624’s Write Only Registers, or a single byte of data read out from one of the CMX624’s Read
Only Registers, as illustrated in Figure 7.
Data sent from the µC on the Command Data line is clocked into the CMX624 on the rising edge of the Serial
Clock input. Reply Data sent from the CMX624 to the µC is valid when the Serial Clock is high. The interface
is compatible with the most common µC serial interfaces such as SCI, SPI and Microwire, and may also be
easily implemented with general purpose µC I/O pins controlled by a simple software routine. See Figure 10
for detailed ‘C-BUS’ timing requirements.
Figure 7 ‘C-BUS’ Transactions
2001 Consumer Microcircuits Limited
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