RC96V24DP
2.0 Hardware Interface
Single Device Data/Modem Data Pump
D96V24DSA
2-7
RS0-RS4
IA
PARALLEL MICROPROCESSOR INTERFACE (con’t)
Register Select Lines. The five active high Register Select inputs (RS0 - RS4) address
Interface memory registers in the modem when CS is low. These lines are typically
connected to address lines A0-A4 to address one of 32 8-bit internal interface memory
registers (00-1F). The selected register can be read from, or written into, via the 8-bit
parallel data bus (DO-D7).
READ
WRITE
IAIA
Read Enable and Write Enable. Reading or writing is controlled by the host pulsing
either READ or WRITE input low, respectively, during the microprocessor bus access
cycle.
During a write cycle, data from the data bus is copied into the addressed DSP interlace
memory register, with high and low bus levels representing one and zero bit states,
respectively.
IRQ
OA
Interrupt Request. The IRQ output structure is an open-drain field-effect-transistor
(FET). The IRQ output can be enabled in the interface memory to allow immediate
indication of change of conditions in the modem. The use of IRQ is optional depending
upon modem application.
HYBRID CIRCUIT
TXA1
TXA2
O(DF)
Transmit Analog 1 and 2. The TXA1 and TXA2 outputs are differential outputs 180
degrees out of phase with each other.
RXA
I(DA)
Receive Analog. RXA is a single-ended receive data input from the telephone line
interface or an optional external hybrid circuit.
VC
OA
Centerpolnt Voltage. VC is a +2.5 VDC centerpoint voltage which serves as the internal
'analog ground' reference point.
TELEPHONE LINE INTERFACE
RADVR
OD
Relay A Driver. RADVR is an open drain output which can directly drive a relay with
greater than 360 Q coil resistance and having a 'must operate' voltage of no greater
than 4.0 VDC.
The RADVR output is controlled by the state of the RA bit, except in pulse dial mode.
When RA is a 1, the RADVR output is active which applies current to the relay coil.
In a typical application, RADVR is connected to the normally open Off-Hook relay. In
this case, RADVR active closes the Off-Hook relay to connect the modem to the
telephone line.
RBDVR
OD
Relay B Driver. RBDVR is an open drain output which can directly drive a relay with
greater than 360 Q coil resistance and having a 'must operate' voltage of no greater
than 4.0 VDC.
RBDVR output is controlled by the state of the RB bit. When RB is a 1, the RBDVR
output is active which applies current to the relay coil.
In a typical application, RBDVR is connected to the normally closed Talk/Data relay. In
this case, RBDVR active opens the relay to disconnect the handset from the telephone
line.
RING
IA
Ring Frequency. A low-going edge on the RING input initiates a ring frequency
measurement. A valid ring detection is indicated by the RI bit.
Table 2-2. Hardware Interface Signal Definitions (Continued)
Label
I/O Type
Signal/Definition
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