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.
Wingfield [Page 1] RFC 12 IMP-HOST INTERFACE FLOW DIAGRAMS 26 August 1969
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 | +---+ +-----------------------+
Wingfield [Page 2] RFC 12 IMP-HOST INTERFACE FLOW DIAGRAMS 26 August 1969
+---+ +---+
| 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 |
+---+ +---------------------+
Wingfield [Page 3] RFC 12 IMP-HOST INTERFACE FLOW DIAGRAMS 26 August 1969
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 | +---+
Wingfield [Page 4] RFC 12 IMP-HOST INTERFACE FLOW DIAGRAMS 26 August 1969
+---+
| 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]
Wingfield [Page 5] RFC 12 IMP-HOST INTERFACE FLOW DIAGRAMS 26 August 1969
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