16-30
MCF5272 User’s Manual
Operation
Figure 16-30. Multidrop Mode Timing Diagram
A character sent from the master station consists of a start bit, a programmed number of
data bits, an address/data (A/D) bit flag, and a programmed number of stop bits. A/D = 1
indicates an address character; A/D = 0 indicates a data character. The polarity of A/D is
selected through UMR1n[PT]. UMR1n should be programmed before enabling the
transmitter and loading the corresponding data bits into the transmit buffer.
In multidrop mode, the receiver continuously monitors the received data stream, regardless
of whether it is enabled or disabled. If the receiver is disabled, it sets the RxRDY bit and
loads the character into the receiver holding register FIFO stack provided the received A/D
bit is a one (address tag). The character is discarded if the received A/D bit is zero (data
tag). If the receiver is enabled, all received characters are transferred to the CPU through
the receiver holding register stack during read operations.
In either case, the data bits are loaded into the data portion of the stack while the A/D bit is
loaded into the status portion of the stack normally used for a parity error (USRn[PE]).
Detection of breaks and framing or overrun errors operates normally. The A/D bit replaces
the parity bit, so parity is neither calculated nor checked. Messages in this mode may still
contain error detection and correction information. If 8-bit characters are not required,
software can be used to calculate parity and append it to the 5-, 6-, or 7-bit character.
ADD1
TxD
Transmitter
Enabled
USRn[TxRDY]
C0
ADD2
1
1
internal
module
select
A/D
A/D
A/D
ADD1
RxD
Receiver
Enabled
USRn[RxRDY]
C0
ADD2
1
1
internal
module
select
A/D
A/D
A/D
0
A/D
0
A/D
(C0)
Status Data
(ADD 2)
Status Data
ADD 1
Peripheral Station
Master Station
UMR1n
[PM] = 11
UMR1n[PM] = 11
UMR1n[PT] = 1
ADD 1
UMR1n[PT] = 0
C0
UMR1n[PT] = 2
ADD 2
UMR1n[PM] = 11
Summary of Contents for DigitalDNA ColdFire MCF5272
Page 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Page 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Page 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Page 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Page 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Page 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Page 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Page 338: ...13 44 MCF5272 User s Manual Application Examples ...
Page 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Page 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Page 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Page 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...