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MCF5282 User’s Manual
MOTOROLA
Operation
register and loaded into the top empty receiver holding register position of the FIFO. Thus,
data flowing from the receiver to the CPU is quadruple-buffered.
In addition to the data byte, three status bits, parity error (PE), framing error (FE), and
received break
(RB), are appended to each data character in the FIFO; OE (overrun error)
is not appended. By programming the ERR bit in the channel’s mode register (UMR1
n
),
status is provided in character or block modes.
USR
n
[RxRDY] is set when at least one character is available to be read by the CPU. A read
of the receive buffer produces an output of data from the top of the FIFO stack. After the
read cycle, the data at the top of the FIFO stack and its associated status bits are popped and
the receiver shift register can add new data at the bottom of the stack. The FIFO-full status
bit (FFULL) is set if all three stack positions are filled with data. Either the RxRDY or
FFULL bit can be selected to cause an interrupt or DMA request.
The two error modes are selected by UMR1
n
[ERR] as follows:
• In character mode (UMR1
n
[ERR] = 0, status is given in the USR
n
for the character
at the top of the FIFO.
• In block mode, the USR
n
shows a logical OR of all characters reaching the top of
the FIFO stack since the last
RESET
ERROR
STATUS
command. Status is updated as
characters reach the top of the FIFO stack. Block mode offers a data-reception speed
advantage where the software overhead of error-checking each character cannot be
tolerated. However, errors are not detected until the check is performed at the end of
an entire message—the faulting character is not identified.
In either mode, reading the USR
n
does not affect the FIFO. The FIFO is popped only when
the receive buffer is read. The USR
n
should be read before reading the receive buffer. If all
three receiver holding registers are full, a new character is held in the receiver shift register
until space is available. However, if a second new character is received, the contents of the
the character in the receiver shift register is lost, the FIFOs are unaffected, and USR
n
[OE]
is set when the receiver detects the start bit of the new overrunning character.
To support flow control, the receiver can be programmed to automatically negate and assert
URTS
n
, in which case the receiver automatically negates URTS
n
when a valid start bit is
detected and the FIFO stack is full. The receiver asserts URTS
n
when a FIFO position
becomes available; therefore, overrun errors can be prevented by connecting URTS
n
to the
UCTS
n
input of the transmitting device.
NOTE
The receiver can still read characters in the FIFO stack if the
receiver is disabled. If the receiver is reset, the FIFO stack,
URTS
n
control, all receiver status bits, and interrupts, and
DMA requests are reset. No more characters are received until
the receiver is reenabled.
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...