82551QM Datasheet, PDF (49/120 Pages) Intel Corporation – Fast Ethernet Multifunction PCI/CardBus Controller

Networking Silicon — 82551QM
7.0
7.1
7.2
Modem Functionality
The local port mimics the standard 8-bit interface of a modem to the host system and emulates a
16550 Universal Asynchronous Receiver/Transceiver (UART) modem interface. The modem
interface includes the following:
• 8-bit data bus: FLD7:0
• Control signals: AEN (FLCS#), MCNTSM# (FLA12), MINT (FLA11), MRING# (FLA10),
MRST (FLA9), RD# (FLOE#), and WR# (FLWE#)
• 4 address lines
PCI Address Mapping to the Modem
The modem can be accessed by the PCI bus through either I/O or memory mapping.
Modem Read and Write Cycles
Basic read/write cycles to the modem device are shown in the figure below.
Modem AEN (CS#)
Modem Addrsess
Modem Data In / Out
Modem IOCHRDY
Modem WE# / RD#
t2
t1
t4
Figure 13. Modem Read/Write Cycles
t8
t6'
t6
t9
t10
t3
t5
t7
t11
7.3
Modem and Preboot eXtension Environment Coexistence
The 82551QM local bus can interface with a Flash device or modem without external support.
External logic can be implemented on the circuit board to support both devices by using the
Modem Chip Select (MDMCS#) and Flash Chip Select (FLCS#) signals.
Datasheet
43