TM 5-6675-320-14
Table 4-15. REGISTER FUNCTIONS
R e g i s t er
Operation
Function
20
21
22
23
24
25
26
27
Read Self-Test
W r i t e S e l f - T e s t
Read Confidence Test
Write to HP-IB Interface
Read HP-IB
Write HP-IB
Read Front Panel & Paper
Advance
Write to Paper Advance
Not Used
I n h i b i t I n t e r r u p t
E n a b l e I n t e r r u pt
Read Front Panel
Write Front Panel
Read Front Panel
Write Front Panel
w. MOS and TTL bus drivers.
The MOS and TTL bus drivers are 3-state bidirec-
tional bus drivers (BIBs) which provide a two-way data transmission between the
microprocessor and the various circuits of the plotter.
BIBs U46 and U47 buffer the
microprocessor bus from the MOS bus which interfaces with the memory circuits and
the TTL BIBs.
These BIBs are enabled by delayed extended synchronous memory com-
plete (DXSMC).
The direction that these BIBs are driving is controlled by the
microprocessor generated processor driving (PDR). When PDR is low, the BIBs drive
out to the bus, and with PDR high, the BIBs drive toward the microprocessor.
Further buffering is provided for the HP-IB circuitry and the front panel by the
BIBs U49 and U50.
Direction control for these BIBs also comes from PDR, while
the enable signal is generated in the memory timing circuits.
4-128
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
