APPLICATION NOTE:    1


SUBJECT��            HDC/DM�� operatio� wit� Nort� Sta� 32ˠ an� �
                     HRAM dynamic memory boards. 


PRODUCT:             HDC/DMA Controller


DATE:                May 12, 1982




BACKGROUND:

Th� HDC/DM� controlle� generate� memor� rea� cycle� i� accordanc� �
wit� th� IEE� 69� standard� fo� th� S-10� bus��  Thes� standard� �
stat� tha� th� statu� line� (SW� � an� SMEM� i� particular�� ar� �
fo� decodin� o� statu� an� ar� no� t� b� use� a� strobe� t� begi� �
memor�� cycles�� Sinc� th� HDC/DM� i� eithe� readin� fro�� o� �
writin� t� th� bu� (bu� no� both� durin� dat� transfers�� i�� i� �
no� necessar� fo� i� t� chang� th� statu� line� betwee� eac� bu� �
cycle. 

Memor�� board� whic� compl� wit� th� IEE� 69�� tak� thi� int� �
accoun�� an� therefor� us� onl� th� strobe� (pDBI� o� /pWR�� t� �
initiat� � memor� cycle�  Som� olde� desig� dynami� memor� board� �
(i� fac�� � goo� dea� o� them� us� th� risin� edg� o� sMEMҠ t� �
begi� � memor�� cycle��  Thi� wil� caus� � proble�� sinc� th� �
HDC/DM� maintain� � leve� o� thi� line��  Fortunatel� ther� i� � �
relativel� simpl� solutio� t� thi� problem.


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�MODIFICATIONS:

B�� addin� � wai�� stat� o� al� DM�� read� b�� th� HDC/DM� �
controller� th� signa� pDBI� wil� b� lengthene� t� allo� � longe� �
acces� tim� fo� dynami� memor� boards� Ther� i� on� dis-advantag� �
t� thi� approac� i� tha� i� increase� th� minimu�� syste�� cloc� �
spee� fo� DM� dat� transfer� fro� 2.� Mh� t� 3.� Mhz�� Thi� wai� �
stat� ca� b� adde� simpl� b� changin� th� PA� (16R8� a� locatio� �
3Ġ� o� th� HDC/DM�� fro�� 3D-Ġ t� on� wit� th堠 3D-NORTH� �
designation�� I�� i� the� necessar� t� jumpe� th� dynami� memor� �
boar� t� us� th� strob� pDBI� rathe� tha� sMEMҠ fo� initiatin� �
memor�� rea� cycles�� Agai� thi� i� � relativel� simpl� mo�.  



Fo� NORT� STA� 32� memor� boards:


     1�   Remov� chi� locate� a� 4� o� th� NORT� STA� 3� � memor� �
          board (74LS02).

     2�   Usin� � shor� piec� o� 3� g� jumpe� wire� connec� pi� � �
          of 4C to pin 8 of 4C.

     3��  Ben� o� cu�  pi� � o� 4� s� i� doe� no�� mak� contac� �
          wit� th� socke�� an� re-inser� chi� bac� int� it� �
          socket.

Th� memor�� boar� wil� no� functio� wit� NORT� STA� product� a� �
well as DM� board� conformin� t� th� IEEE 696 standard� 




For NORTH STAR HRAM memory boards:

Ther� i� n� hardwar� modificatio� require� o� HRA� board� a� the� �
us� th� pDBI� signal�  Simpl� remov� I� 3D-� o� th� HDC/DM� boar� �
an� replac� i� wit� chi� wit� designatio� 3D-NORTH*��  Th� board� �
wil� no� b� compatible�