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3.4 THE SERIAL COMMUNICATION CHANNELS
The SBC5206 offers a number of serial communications. They are discussed in this section.
3.4.1 The MCF5206 DUART
The MCF5206 has two built in UART’s, These serial channels with software programmable baud rate
generators are not used by the SBC5206 or dBUG and are available to the user. The dBUG, however,
programs the interrupt level for UART1 to Level 3, priority 2 and autovector mode of operation. The
interrupt level for UART2 to Level 3, priority 1 and autovector mode of operation. The signals of these
channels are available on J7. The signals of UART1 are also passed through the RS-232 driver/receiver
and are available on DB-9 connector J6. Refer to the MCF5206 User’s Manual for programming and the
register map.
3.4.2 MC68HC901
To provide the board with one independent serial communication channel for dBUG communication with
terminal or PC, an MC68HC901 is used. This device provides four timer channels (A, B, C, and D), one
serial communication channel, and 8 input lines. Channel D timer is used as the baud rate generator for
the serial communication channel.
The clock source for the timers is the 2.4576MHZ crystal. The clock signal to drive the MC68HC901
logic is one-fourth of the processor’s clock.
The TXD (SO) signal and the RXD (SI) signal are passed through RS-232 driver/receiver and are
available on J5. The eight input lines are used to report the ISA Bus interrupts (IRQ3, IRQ4, IRQ5,
IRQ6, IRQ7, IRQ9, IRQ10, and IRQ11). The interrupt from MC68HC901 is reported to MCF5206 on -
IRQ4 of the MCF5206. The interrupt level for the MC68HC901 is set for Level 4 with priority 2. The
vectors used for MC68HC901 are $F0 to $FF. It generates 16 vectors. This should not be changed.
The -CS2 is used to access the MC68HC901 internal registers, it is mapped to $30000000. The -CS1 is
programmed to generate an Interrupt Acknowledge signal to drive the -IACK of the MC68HC901. Refer
to MC68HC901 User’s Manual for functional description and the programming model.
3.4.3 Motorola Bus (M-Bus) Module
The MCF5206 has a built in M-Bus module which allows interchip bus interface for a number of I/O
devices. It is compatible with industry-standard I
2
C Bus. The SBC5206 does not use this module and it
is available to the user. The two M-Bus signals are SDA and SCL which are available at J7 connector.
These signals are open-collector signals. However, they have pull-up resistors on the SBC5206. The
interrupt control register for M-Bus is set for Level 3, priority 0 and autovector.
3.5 THE PARALLEL I/O Port
The MCF5206 has one 8-bit parallel port. All the pins have dual functions. They can be configured as
I/O or their alternate function via the Pin Assignment register. All pins are configured as I/O pins.