IMP-Host interface flow diagrams

Network Working Group M. Wingfield Request for Comments: 12 REVISED 26 August 1969

IMP-HOST INTERFACE FLOW DIAGRAMS

The following flow diagrams were extracted from the logic diagrams provided in Appendix B of BBN Report No. 1822. These diagrams indicate the logical sequence of hardware operations which occur within the IMP-HOST interface. The logic names appearing in the blocks correspond to the logic elements found in Appendix B.

IMP to HOST Message +----------+ | Start | | Input | +----------+ | V +------------------------+ | LAST <--0; IMPERR <--0 | | PAD <--0; IN REQST <--0| | COUNTER <--0 | +------------------------+ +---+ |<----------------- | B | V +---+ +--------------+ | RFNIB <-- 1 | +--------------+ |<--------------+ V | / \ | / \ | / THERE'S \ N | \YOUR BIT /----------+ \=1 ? / \ / | +------------------->V | / \ +----+------+ N / \ | IMP ERROR |<------ / IMP \ | <--- 1 | \ READY / +-----------+ \ ? / \ / | Y V / \ / \ +-----------+ Y / LAST \ | PAD <-- 1 |<-------\ IMP BIT / +-----------+ \ =1? / | \ / +---+ +------------------->|<-----------------| C | V +---+ +-----------------------+ | PULSE SHIFT REG. | +---+ | INCREMENT COUNTER |------>| A | | RFNTR <-- 0 | +---+ +-----------------------+

+---+ +---+ | C | | A | +-+-+ +-+-+ ^ | | Y V / \ / \ / \ N /WORD \ / PAD=1 \ <--------/ LENGTH \ \ ? / \ =1 / \ / \ ? / \ / \ / | N | V V +---+ +----------------------+ | B | | INREQST <--1 | +---+ +----------------------+ |<-----------+ V | / \ | /DATA \ | /HAS BEEN \_N_____| \ TAKEN / \ ? / \ / V Y +----------------------+ | INREQST <--0 | +----------------------+ V / \ / \ +------------+ / LAST = 1\----------->| END OF | \ ? / | MESSAGE | \ / +------------+ \ / ^ | N | V | / \ | / \ | / PAD = 1 \-------------------+ \ ? / \ / \ / | N V +---+ +---------------------+ | B |<---------| CLEAR COUNTER | +---+ +---------------------+

HOST TO IMP MESSAGE

+--------------+ | START OUTPUT | +------+-------+ V +------------------------+ | COUNTER <-- 1 | | LSTWD <--0; BTAVL <--0 | +-----------+------------+ +---+ |<--------------------| C | V +---+ +-----------+------------+ | OUT REQST <-- 1 | | CLEAR SHIFT REG. | +-----------+------------+ +------------>| | V | / \ | N / \ |_______ / STROBE \ \DATA WORD/ \ =1 ?/ \ / V Y +------------+------------+ | LOAD SHIFT REGISTER | | OUTREQST <-- 0 | | COUNTER <-- 1 | +-------------------------+ +---------->| | V | / \ | / \ |N / RFNBIT \ +----- \ = 1 / \ ? / +----------+ \ / | | N V Y | / \ +--------+--------+ V / \ | THERE'S YOUR |----------->/ RFNBIT \ | HOST BET <-- 1 | \ = 0 / +-----------------+ \ ? / \ / | Y +-+-+ | A | +---+

+---+ | A | +---+ V +--------------+-------------+ | THERE'S YOUR HOST BIT <--0 | | BTAVL <-- 0 | +----------------------------+ V / \ / \ / WORD\ Y / \ Y /LENGTH -1\---------->/ LSTWD \---+ \ = 1 / \ = 1 / | \ ? / \ ? / | \ / \ / | | N | N | V | | / \ | | / WORD\ | V ________________ / LENGTH \ | +------------+ | \ = 1 / | | LIBIT <- 1 | | \ ? / | +------------+ | \ / V | | |<-----------------------<------+ | V | +-----------------+ | | PUSH SHIFT REG. | +-------------+ |INCREMENT COUNTER| | LIBIT <-- 0 | +-----------------+ +-------------+ V | +---+ | | B | V +---+ / \ / \ / LSTWD \ Y +-------------+ \ = 1 /--------------------------->| END OF | \ ? / | MESSAGE | \ / +-------------+ | N V +---+ | C | +---+

[ This RFC was put into machine readable form for entry ] [ into the online RFC archives by Lorrie Shiota]

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