CMX850L8 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX850L8' PDF : 103 Pages View PDF
Communications Controller
CMX850
CBUSCON Register b2: IRQ
This bit is an inverted form of the IRQN output from the modem that is connected to the 8051 µC’s
Int3 interrupt input. This register bit is read-only.
b2 = 1 IRQN active
b2 = 0 IRQN inactive
CBUSCON Register b1: Reserved bit for internal use.
This bit is reserved for internal use; its value when read will be indeterminate.
CBUSCON Register b0: C-BUS select
This bit must be set active to enable a transaction between the 8051 µC and the modem, and taken
inactive between transactions. A C-BUS transaction comprises a command byte being sent to the
modem, followed by the transfer of up to two further bytes to/from the modem.
b0 = 1 C-BUS select active
b0 = 0 C-BUS select inactive
1.5.9.2 C-BUS Buffer Register (CBUSBUF)
CBUSBUF: SFR Address $EB
All bits are cleared to 0 on reset
Bit:
7
6
5
4
3
2
1
0
Bits 7-0 of buffer data
CBUSBUF Register b7-0: C-BUS data buffer
Data written to this buffer immediately gets shifted out to the modem via the C-BUS interface, and
is replaced by reply data from the modem. When reading data from the modem, an instruction
(single cycle minimum) must be inserted between a CBUSBUF dummy write and the CBUSBUF
data read.
© 2003 CML Microsystems Plc
43
D/850/6
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