MC68MH360ZP33L Freescale Semiconductor, MC68MH360ZP33L Datasheet - Page 521

• Manufacturer Part Number: MC68MH360ZP33L
• Description: IC MPU 32BIT QUICC 357-PBGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68MH360ZP33L

• Processor Type: M683xx 32-Bit
• Speed: 33MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 357-PBGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -

7.10.19.1 LOCALTALK BUS OPERATION. The following paragraphs detail the operation
of the LocalTalk. A LocalTalk frame is a modified HDLC frame as shown in Figure 7-61.
First, a synchronization sequence of greater than three bits is sent. This sequence consists
of at least one logical one bit, FM0 encoded, followed by greater than two bit times of line
idle. No particular maximum time is specified for this line idle time. The idle time allows some
LocalTalk equipment to sense carrier by detecting a "missing clock" on the line.
The remainder of the frame is a typical half-duplex HDLC frame. Two or more flags are sent,
allowing bit, byte, and frame delineation/detection. Two bytes of address, destination and
source, are transmitted next. This is followed by a byte of control and 0 to 600 data bytes.
Next, two bytes of CRC are sent. The CRC is the common 16-bit CRC-CCITT polynomial
referenced in the HDLC standard protocol. The LocalTalk frame is then terminated by a flag
and a restricted HDLC abort sequence (a sequence of 12 to 18 logical ones). The transmit-
ter's driver is then disabled.
The control byte within the LocalTalk frame indicates the type of frame. Control byte values
from 0x01 to 0x7f are data frames, and control byte values from 0x80 to 0xff are control
frames. Four different control frames are currently defined: ENQ (Enquiry), ACK (ENQ
acknowledgement), RTS (request to send a data frame), and CTS (clear to send a data
frame).
Frames are sent in groups known as dialogs. For instance, to transfer a data frame, three
frames are actually sent over the network: an RTS frame (not to be confused with the RS-
232 pin RTS) is sent requesting the network, a CTS frame is sent by the destination node,
and the data frame is sent by the requesting node. These three frames comprise one pos-
sible type of dialog. Once a dialog has begun, other nodes cannot begin transmission until
the dialog is complete. Dialogs are typically handled in software.
Frames within a dialog are transmitted with a maximum interframe gap (IFG) of 200 s.
Although the LocalTalk specification does not state it, there is also a minimum recom-
mended IFG of 50 s. Dialogs must be separated by a minimum interdialog gap (IDG) of 400
MOTOROLA
s. In general, these gaps are implemented via software.
SYNC
SEQ
BITS
> 3
FLAGS
HDLC
BYTES
MORE
2 OR
The MC68302 also provides the same general level of LocalTalk
functionality when it is combined with its companion chip, the
MC68195 LocalTalk Adaptor (LA). The LA device, however, is
not required with the QUICC.
ADDR.
DEST.
BYTE
1
Freescale Semiconductor, Inc.
SOURCE
ADDR.
BYTE
Figure 7-61. LocalTalk Frame Format
For More Information On This Product,
1
CONTROL
BYTE
BYTE
1
MC68360 USER’S MANUAL
Go to: www.freescale.com
NOTE
(OPTIONAL)
0–600 BYTES
DATA
Serial Communication Controllers (SCCs)
CRC-16
BYTES
2
CLOSING
FLAG
BYTE
1
SEQUENCE
ABORT
12–18
ONES
7-197