HI-6135 Datasheet, PDF (95/172 Pages) Holt Integrated Circuits – 40 MHz SPI Host Interface

HI-6135
When the NOTICE2 bit is logic 1 in the “Remote Terminal Configuration Register (0x0017)”, broadcast message data
is stored in a broadcast data buffer assigned for the subaddress or mode command. Each subaddress or mode com-
mand must have an assigned, valid non-zero broadcast buffer address. Non-broadcast message data is stored in Data
Buffer A.
There are two ways to deal with broadcast messages in indexed buffer mode:
Option 1 for Index Mode Broadcast Messages:
The first alternative isolates broadcast message information in the broadcast data buffer. If the descriptor Control Word
IBR bit and “Remote Terminal Interrupt Enable Register (0x0012)” IBR bit are both set, reception of broadcast mes-
sages generates an INT interrupt to the host. The broadcast data buffer must be processed before another broadcast
message arrives to prevent loss of data. Broadcast messages do not decrement the INDX register, and Data Pointer
A is not updated in message post-processing. This scheme may be well suited for Single Message Mode (INDX = 0)
when the host can reliably service either the broadcast data buffer or data buffer A before the next receive message
arrives for the same subaddress (or mode code).
Option 1 Setup: At initialization, host asserts NOTICE2 bit in the “Remote Terminal Configuration Register (0x0017)”
and sets the Control Word IBR (Interrupt Broadcast Received) bit for each index mode descriptor block. The IBR bit is
also asserted in the “Remote Terminal Interrupt Enable Register (0x0012)”.
When a broadcast command is received, message information and data are stored in the broadcast data buffer. If
descriptor Control Word IBR bit is set, an INT interrupt is generated. The host must read the Interrupt Log to determine
the originating subaddress (or mode code) then service the broadcast data buffer for that subaddress (or mode code)
before the next broadcast message to the same subaddress (or mode code) arrives.
Option 2 for Index Mode Broadcast Messages:
The second alternative stores both broadcast and non-broadcast message information in data buffer A. Optional IBR
interrupts can signal arrival of broadcast messages. The RT handles broadcast messages just like non-broadcast
messages, except the Message Information Word BCAST bit is asserted to identify broadcast messages during host
buffer servicing. All messages decrement the INDX register and Data Pointer A is updated in message post-process-
ing. This scheme is compatible with Single Message Mode or conventional N-message indexing. For Notice II compli-
ance, separation of broadcast and non-broadcast data occurs within the host.
Option 2 Setup: At initialization, host negates the NOTICE2 bit in the “Remote Terminal Configuration Register
(0x0017)”. If broadcast interrupts are used, the Control Word IBR (Interrupt Broadcast Received) bit is asserted at
each desired index mode descriptor block. The IBR bit is also asserted in the “Remote Terminal Interrupt Enable
Register (0x0012)”.
Using option 2, the host has several options for servicing data buffer A: (a) when INDX decrements from one to zero
(using the IXEQZ interrupt), (b) when a broadcast message occurs (using the IBR interrupt) or (c) when any message
arrives (using the IWA interrupt).
HOLT INTEGRATED CIRCUITS
95