CME8000-BUS-LP-04 C-Max, CME8000-BUS-LP-04 Datasheet - Page 9

• Manufacturer Part Number: CME8000-BUS-LP-04
• Description: MOD BUS PCB W/RS485 ANT FULL DUP
• Manufacturer: C-Max

Specifications of CME8000-BUS-LP-04

• Frequency: 40kHz ~ 120kHz
• Sensitivity: -115dBm
• Modulation Or Protocol: UTC - Universal Time Code
• Applications: Radio Controlled Time
• Current - Receiving: 2mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: On-Board, Wire Antenna
• Voltage - Supply: 2.7 V ~ 5 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Memory Size: -
• Data Rate - Maximum: -

Data Sheet
5.
The data-link layer of the software defines the information that moves across the bus in any given
packet. The bytes defined in the data-link layer do not necessarily have a one-to-one correlation with
the bytes in the physical layer. Many physical devices, such as I
that implement the functions of some of the bytes in the data-link layer. This data-link layer is
intended to be generic so that it and the application layer of the software will not need to change even
if the physical device must be redesigned. This layer of the communication system is appropriate for
such technologies as a UART multi-drop environment.
CME8000-
SPEC No.
4. Communications and Collision Detection Protocol
The communications subsystem will use a collision detection scheme to determine when the
communications port is free or in use and when a collision has occurred. A collision occurs when
two or more masters attempt to use the communications bus at the same time. This can be
detected because the transmit and receive ports on the micro controller are connected to the same
bus wire, albeit through additional circuitry. Careful control of the interrupts associated with the
communications port will allow this to be an interrupt driven activity. Logically, this is a byte-
oriented protocol. A higher level protocol determines the length and content of packets comprising
messages.
The following state table describes the function of the collision detection protocol.
Data-Link Layer
BUS
In the two delay states, 5 and 6, a byte time is defined as the amount of time required to
transmit a single byte on the communications bus. This time is determined by the baud rate,
number of data bits, number of stop bits, and a parity bit, if used.
The variable delay period shown in state five is intended to make the restart delay time
random. If a collision does occur, the two bus masters will not delay the same amount of time
before retrying transmission. This will reduce the possibility of subsequent collisions by the
two masters. The variable delay period could be determined by a pseudo random number
process, or by board function.
CME8000-BUS
Revision
B6
Stat
e
1
2
3
4
5
6
Table 1. Physical Communication Protocol State Table
Action
Are there bytes to send?
Check bus activity
Send Byte
Does byte sent = byte
received?
Delay 3 to 8 byte times
Delay 5 byte times
26.07.05
State
C-MAX printed
26.07.2005
Result
Yes
No
Busy
Free
Yes
No
Complete
Complete
2
C, have bits in the physical layer
English
Version
Next
State
2
1
6
3
4
1
5
1
1
C-MAX
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