
RISC Microcode from RAM
MOTOROLA
MC68302 USER’S MANUAL
C-3
C.3 CENTRONICS
With this package, SCC2 is turned into an interface that can receive Centronics data. This
package, for example, could be used in a laser printer design requiring a Centronics inter-
face option. The package uses SCC2 (its pins and registers) in addition to PA12, PA13 or
PA11, PA14, and PA15.
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RECEPTION CONTROLLER
The main features are as follows:
Flexible Message-Oriented Data Structure
Flexible Control Character Comparison
Controls the BUSY and ACK Signals
Three Timing Relationships Possible between BUSY and ACK
Supports the SET_BUSY and CLEAR_BUSY Commands
Programmable Duration (in clock cycles) of the ACK Signal
Receive Buffer May Be Closed upon a Programmable Silence Period
C.4 PROFIBUS CONTROLLER
Process field bus (PROFIBUS) is a UART-based master-slave protocol that specifies data
rates starting at 9.6 kbps. The PROFIBUS microcode running on the IMP RISC controller
assists the M68000 core in handling some of the time-critical PROFIBUS link layer func-
tions, leaving more of the M68000 core available for the application software.
The main PROFIBUS controller features are as follows:
Automatic Frame Synchronization by Searching for the Start Delimiter
Frame Preceding IDLE Sequence Generation/Checking
Flexible Frame-Oriented Data Buffers
Separate Interrupts for Frames and Buffers (Receive and Transmit)
Maintenance of Six 16-Bit Error Counters
Two Address Comparison Registers with Mask
Frame Error, Noise Error, Parity Error Detection
Detection of IDLE in the Middle of a Frame
Check Sum Generation/Checking
End Delimiter (ED) Generation/Checking
Three Commands
C.5 AUTOBAUD SUPPORT PACKAGE
The package allows a UART to automatically detect the baud rate of a serial stream and ad-
just to it. This is useful in modem applications that must support an autobaud capability. It is
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Centronics is a trademark of Centronics.