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4.5.15.10 V.110 MASK REGISTER.
The SCC mask register (SCCM) is referred to
as the V.11 O mask register when the SCC is operating as a V. 11 O controller.
It is an 8-bit read-write register that has the same bit format as the V. 110
event register. If a bit in the V.110 mask register is a one, the corresponding
interrupt in the event register will be enabled. If the bit is zero, the corre-
sponding interrupt in the event register will be masked.
4.6 SERIAL COMMUNICATION PORT (SCP)
4-110
The SCP is a full-duplex, synchronous, character-oriented channel that pro-
vides a three-wire interface (receive, transmit, and clock). The SCP consists
of independent transmitter and receiver sections and a common clock gen-
erator. The transmitter and receiver sections use the same clock, which is
derived from the main clock by a separate on-chip baud rate generator. Since
the MC68302 is an SCP master for this serial channel, it generates both the
enable and the clock signals.
The SCP allows the MC68302 to exchange status and control information
with a variety of serial devices, using a subset of the Motorola serial periph-
eral interface (SPI). These devices include industry-standard CODECs as well
as other microcontrollers and peripherals.
The SCP enable signals, which can be implemented using the general-pur-
pose 1/0 pins, are used to enable one of several potential SCP slave devices.
The clock signal (SPCLK) shifts the received data (SPRXD) in and shifts the
transmitted data (SPTXD) out. The clock is gated; it operates only while data
is being transferred and is idle otherwise.
The SCP can be configured to operate in a local loopback mode, which is
useful for local diagnostic functions.
Note that the least significant bit of the SCP is labeled as data bit 0 on the
serial line; whereas, other devices, such as the MC145554 CODEC, may label
the most significant bit as data bit 0. The MC68302 SCP bit 7 (most significant
bit) is shifted out first.
The SCP key features are as follows:
• Three-Wire Interface (SPTXD, SPRXD, and SPCLK)
• Full-Duplex Operation
• Clock Rate up to 4.096 MHz
• Programmable Baud Rate Generator
• Local Loopback Capability for Testing
MC68302 USER'S MANUAL
MOTOROLA
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