HP 13255 Technical Information page 25

132SS
Cartridge Tape Module
13255-91032/23
Rev AUG-01-76
signal for the status drivers. The TACH/2 signal is delayed one cycle
of SYS CLK
by U28,
Pin
5
and is then exclusive-ORed to produce DTACH/2
at U29, Pin 8. OTACH/2 produces a pulse at each transition of TACH/2
with a width equal to one cycle of
SYS
CLK.
3.0.7 STATUS DRIVERS - CTU INTERFACE PCA.
3.0.7.1 The status drivers present status information for the mOdule to the
terminal bus.
3.0.7.2 The CINO, CINt, RIP, and INTERRUPT signals are gated onto the terminal
bus
by
U31 which is enabled by STATUS EN. The signals are inverted on
the bus to provide ground true logic levels. The TACH, HOLE, GAP, and
BYTE ROY Signals are gated onto the terminal bus by U12 whiCh is en-
abled
by
STATUS
E~.
3.0.8 INTERRUPT LOGIC - CTU INTERFACE PCA.
3.0.8.1 The interrupt logic provides an interrupt when a transItion occurs in
th~
TACH/2 signal, when a hole is present, or when a byte of data must
be received or sent from the processor.
3.0.8.2 The DTACH/2 signal sets flip-flop U25, causing Pin 9 to be low wnen a
transition occurs in TACB/2. The CLRINT Signal from tne command logic
resets U25, causing Pin 9 to go high. The DHOL signal
s~ts
flip-flop
U25, causing Pin 7 to be low, and indicates the presence of a hole 1n
the tape. The CLRINT signal resets
U2~,
causing Pin 7 to go high.
When U25, Pin 9 is low or U25, Pin 7 is low or BYTE ROY is low, or some
combination of these events occurs, then INTERRUPT will be hiqh. This
causes AfN2 to be
lo~
thereby indicating an interrupt condition to the
processor. If U25, Pin 7 is h1qh and BYTE ROY is high, then no inter-
rupt condition exists and INTERRUPT will be
lo~.
3.1 FUNCTIUNAL DESCRIPTION - READ/WRITE PCA. Refer to the block diagram
(fiqure 4), schematic diagram (figure 5), component location diagram
(fiqure 6), and parts list (02640-60032) located In the appendix.
The Read/Write PCA contains circuitry to record flux transitions onto
cartridges In either CTU Transport, to convert flux transitions re-
corded on the cartridqes into TTL signal levels, and to detect the