RC56D, RC336D, and RC144D Modem Device Sets Designer’s Guide
1154
Conexant
3-11
Table 3-5. MCU Pin Signal Definitions
Label
I/O Type
Signal Name/Description
SYSTEM
XTLI,
XTLO
Ix,
Ox
MCU Crystal/Clock In and Crystal Out. Connect XTLI and XTLO to an external 28.224 MHz crystal
circuit.
CLKOUT
Ot1.6
Clock Output. 28.224 MHz output clock for MDP. Connect to MDP CLKIN pin.
~RES
Is1
MCU Reset. The active low ~RES input resets the MCU logic, and restores the saved configuration from
NVRAM or returns the modem to the factory default values if NVRAM is not present.
~RES low holds the modem in the reset state; ~RES going high releases the modem from the reset
state. After application of VDD, ~RES must be held low for at least 15 ms after the VDD power reaches
operating range. The modem device set is ready to use 25 ms after the low-to-high transition of ~RES.
For serial Interface, the ~RES input is typically connected to a reset switch circuit and to MDP ~RES1 &
~RES2.
For parallel Interface, connect ~RES input to the host bus RESET line through an inverter and to MDP
~RES1 & ~RES2.
~WKRESOUT
(PB6)
Ot1.6
Wake-up Reset. The MCU resets ~WKRESOUT low to indicate that it is busy initializing the modem
after power up or reset. The MCU sets ~WKRESOUT high upon completion of this initialization. Connect
to the MDP ~WKRES pin.
VDD
PWR
Digital Supply Voltage. Connect to VCC (+5V ±5%, filtered).
GND
GND
Digital Ground. Connect to digital ground.
VD3.3
PWR
+3.3 VDC MDP Power. +3.3 VDC power output for MDP. Connect to MDP VDD.
~NMI
Is2pu
Non-Maskable Interrupt. Not used. Connect to VCC.
~TST
Is2pu
Test Mode. Factory test only. Leave open.
~STPMODE (PD3)
It
Stop Mode. Not used. Connect to VCC.
DPIRQ (PD7)
It
MDP Interrupt Request. Connect to the MDP IRQ output.
PARIF (PE6)
Itpu
Parallel/Serial Interface. MCU: PARIF input high (or open) selects parallel host interface; PARIF low
selects serial DTE interface. MCUP: Not used, leave open.
SCPIRQ (PA4)
Itpu
SCP Interrupt Request. If the SCP is used, connect to the SCP IRQ1 output. In serial DTE
configuration, this function is shared with the RXCLK input thus serial synchronous mode cannot be used
if the SCP is connected. Leave open if not used.
~DPRXD (PA5)
It
MDP Received Data. Connect to the MDP RXD output (serial DTE interface only).
EXTERNAL MEMORY BUS INTERFACE
A0-A15,
A16 (PB0),
A17 (PB4)
Ot1.6
Address Lines 0-17. A0-A17 are the external memory bus address lines.
D0-D7
It/Ot1.6
Data Line 0-7. D0-D7 are the external memory bus data lines.
~READ
Ot1.6
Read Enable. ~READ output low enables data transfer from the selected device to the D0-D7 lines.
~WRITE
Ot1.6
Write Enable. ~WRITE output low enables data transfer from the D0-D7 lines to the selected device.
~DPSEL (PB1)
Ot1.6
Modem Data Pump Chip Select. ~DPSEL output low selects the MDP device.
~RAMSEL (PB3)
Ot1.6
RAM Select. ~RAMSEL output low selects the external RAM.
~ROMSEL (PB2)
Ot1.6
ROM Select. ~ROMSEL output low selects the external ROM/flash ROM.
~SCPSEL (PB5)
Ot1.6
SCP Select. ~SCPSEL output low selects the external SCP device.
NVRAM INTERFACE
NVMCLK (PA7)
Ot1.6
NVRAM Clock. NVMCLK output high enables the NVRAM.
NVMDATA (PA1)
It/Ot1.6
NVRAM Data. The NVMDATA pin supplies a serial data interface to the NVRAM.
Содержание RC144D
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