MC68HC58 Motorola, MC68HC58 Datasheet - Page 67

• Manufacturer Part Number: MC68HC58
• Description: Data Link Controller
• Manufacturer: Motorola

5.1 Command Byte
CBR — Command Byte Register
5.1.1 GCOM[7:5] — General Command Field
MC68HC58
TECHNICAL DATA
RESET:
The host MCU and the DLC exchange control and status information through encoded
fields in four types of bytes.
The two byte types containing control information originate in the host MCU. Com-
mand bytes direct a DLC to take certain actions. Configuration bytes determine DLC
operating parameters.
The two byte types containing status information originate in the DLC. Status bytes
convey information concerning DLC buffers and activity to the host MCU. Completion
code bytes convey information concerning J1850 bus arbitration, frame type, and
errors.
The following paragraphs discuss each type of control and status byte in detail. To use
this section, the reader must be familiar with DLC operation and with the interface be-
tween the host MCU and the DLC. Refer to SECTION 4 DATA LINK CONTROLLER
OPERATION for more information on DLC operation. APPENDIX C DLC REGIS-
TERS provides a quick reference to all DLC register bit field encodings.
The values of the fields in a command byte direct the DLC to take specified actions
concerning operating mode, configuration bytes, and the TxFIFO and RxFIFO buffers.
Commands must be latched into the DLC before they are executed.
The host MCU directs the DLC to take certain actions by sending it GCOM command
codes. Table 5-1 is a summary of the general commands. Detailed discussion of each
command follows.
7
0
SECTION 5 CONTROL AND STATUS CODES
GCOM
6
0
CONTROL AND STATUS CODES
5
0
4
0
BTAD
3
0
2
0
1
0
RFC
MOTOROLA
0
0
5-1