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Alto Hardware Manual
Section 5: Miscellaneous Peripherals
36
Note: Connecting an Alto I keyboard to an Alto II or an Alto II Microswitch keyboard to an Alto I
requires rewiring a connector or installing an adaptor cable. An ADL keyboard requires additional logic
to connect to an Alto 1.
5.2 Mouse
The mouse is a hand-held pointing device which contains two encoders which digitize its position as it is
rolled over a table-top.
It also has three buttons which may be read as the three low-order bits of
memory location UfILIN (177030B), in the manner of the keyboard. The bit/button correspondences in
UfILIN are (depressed keys correspond to O's in memory):
UfILIN[13]
UfILIN[14]
UfILIN[lS]
Top or Left Button (RED)
Bottom or Right Button (BLUE)
Middle Button (YELLOW)
The mouse coordinates are maintained by the MRT microcode in locations MOUSELoc(424B)=X and
MOUSELOC+1(42SB)=Y in page one of the Alto memory.
These coordinates are relative, i.e., the
hardware only increments and decrements them.
The resolution of the mouse is approximately 100
points per inch.
5.3 Keyset
The standard Alto includes a five-finger keyset which is presented to the program as S bits of memory
location· UTILIN (177030B), similar to the keyboard. .... The·· bit/key correspondences in UfILIN are
(depressed keys correspond to O's in memory):
UfILIN[8]
UfILIN[9]
UfILIN[10]
UfILIN[ll]
UfILIN[12]
5.4 External Device Interface
Key 0 (left-most)
Key 1
Key 2
Key 3
Key 4 (right-most)
Two memory locations, UTILIN (177030B) and UTlLOUf (1770l6B), provide an interface to external
devices through a connector on the rear of the Alto. If a quantity is stored into UTILOUf, it is latched
and appears as 16 output signals; if a 1 bit is stored; a more negative logic level is generated (TTL "low").
For input, bits 0 to S and bit 7 of UTILIN are available; more positive logic levels (TTL "high") are
reported as 1 bits.
The remaining bits of this location are used by the mouse, keyset and memory
configuration switch.
On the Alto I, this connector also provides various power supply voltages. These are absent on Alto II.
The Alto II provides an additional 16-bit input port (the
x
bus), which can be read by accessing memory
locations 177020B-177023B. The connector on the rear of the Alto II provides the low 2 bits of memory
address and a signal that indicates the
x
bus is being read, together with the 16 input data signals. More
positive logic levels (TIL "high") are reported as 1 bits.
The two sections below describe two common devices connected to UfILIN/UTILOUf, the Diablo HyType
printer and Versatec printer/plotter. The descriptions are for the programmer: the bit values (0 or 1)
refer to values that will be stored into UTlLOUT or read from UfILIN by an Alto program.
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