J1850 Byte Level Protocol Decoder (JBLPD)
10.9 J1850 Byte Level Protocol Decoder (JBLPD)
10.9.1 Introduction
The JBLPD is used to exchange data between the
ST9 microcontroller and an external J1850 trans-
ceiver I.C.
The JBLPD transmits a string of variable pulse
width (VPW) symbols to the transceiver. It also re-
ceives VPW encoded symbols from the transceiv-
er, decodes them and places the data in a register.
In-frame responses of type 0, 1, 2 and 3 are sup-
ported and the appropriate normalization bit is
generated automatically. The JBLPD filters out
any incoming messages which it does not care to
receive. It also includes a programmable external
loop delay.
The JBLPD uses two signals to communicate with
the transceiver:
– VPWI (input)
– VPWO (output)
10.9.2 Main Features
■ SAE J1850 compatible
■ Digital filter
■ In-Frame Responses of type 0, 1, 2, 3 supported
with automatic normalization bit
■ Programmable External Loop Delay
■ Diagnostic 4x time mode
■ Diagnostic Local Loopback mode
■ Wide range of MCU internal frequencies
allowed
■ Low power consumption mode (JBLPD
suspended)
■ Very low power consumption mode (JBLPD
disabled)
■ Don’t care message filter
■ Selectable VPWI input polarity
■ Selectable Normalization Bit symbol form
■ 6 maskable interrupts
■ DMA transmission and reception with End Of
Block interrupts
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