Intel 8XC196Lx - Manual (Page 69)

8-3
J1850 COMMUNICATIONS CONTROLLER
8.2 J1850 CONTROLLER SIGNALS AND REGISTERS
Table 8-1 describes the J1850 controller’s pins, and Table 8-2 describes the control and status
registers.
Table 8-1. J1850 Controller Signals
Signal Type Description
RXJ1850 I Receive
Carries digital symbols from a remote transceiver to the J1850 controller.
TXJ1850 O Transmit
Carries digital symbols from the J1850 controller to a remote transceiver.
Table 8-2. Control and Status Registers
Mnemonic Address Description
J_CFG 1F54H J1850 Configuration
Program this byte register to specify the oscillator prescaler
divisor, mode of operation, and normalization bit format. You must
write to this register during the initialization sequence.
J_CMD 1F51H J1850 Command
Program this byte register to specify the number of bytes to be
transmitted in the next message frame. This register also
monitors the status of the message transmission in progress, and
it can abort, ignore, or retry a message if necessary. Read this
register to determine the status of transmissions in progress.
J_DLY 1F58H J1850 Delay Compensation
Program this byte register to define the length of the delay time
through the external transceiver to compensate for the inherent
propagation delays and to accurately resolve bus contention
during arbitration. You must write to this register during the
initialization sequence.
J_RX 1F52H J1850 Receiver
Read this byte register to receive data in byte increments from the
J1850 bus to the microcontroller CPU. This register is buffered to
allow for reception of a second data byte while the first data byte
is being read.
J_STAT 1F53H J1850 Status
Read this byte register to determine the current status of the
receive and transmit buffers and the J1850 interrupt sources. You
can also determine bus status and in-frame response messaging
status. All bits of this register are cleared when read, with the
exception of the BUS_STAT bit.
J_TX 1F50H J1850 Transmitter
Program this byte register to transmit data in byte increments to
the J1850 bus from the microcontroller CPU. This register is
buffered to allow for writing of a second data byte while the first
data byte is being shifted out.