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3874 Group User’s Manual
HARDWARE
FUNCTIONAL DESCRIPTION
DATA LINK LAYER COMMUNICATION
CONTROL CIRCUIT
The 3874 Group has a built-in data link layer communication con-
trol circuit.
This data link layer communication control circuit is applicable for
multi-master serial bus communication control used only with data
lines through an external driver/receiver.
The data link layer communication control circuit consists of fol-
lowing.
Communication mode register (address 002A16)
Transmit control register (address 002B16)
Transmit status register (address 002C16)
Receive control register (address 002D16)
Receive status register (address 002E16)
Bus interrupt factor discrimination control register (address
002F16)
Control field selection register (address 003016)
Control field register (address 003116)
Transmit/Receive FIFO (address 003216)
This function is realized by hardware and firmware so that com-
munication protocol can be partially modified according to the
user’s specification.
The following are the standard communication rate and functions
which the data link layer communication control circuit can per-
form.
Communication rate:
Approx. 40 kbps
The communication rate depends on
frame or bit protocol.
Synchronous method: Half-duplex asynchronous
Modification method:
PWM method, NRZ, etc.
Communication functions:
Bus arbitration
(CSMA/CD method, etc.)
Error detection
(parity, acknowledge, CRC, etc.)
Frame, data retry
The transmission signal is output from the BUSOUT pin and input
to the BUSIN pin.
Detailed specifications for communication protocol, bit assign-
ment, function, etc. of each register are defined according to each
communication protocol specification confirmation.