HP 13255 Technical Information page 18

13255
Cartridge Tape Module
13255-91032/16
Rev
AUG-01-76
3.0
FUNCTIONAL DESCRIPTION - CTU INTERFACE PCA. Refer to the block diagram
(figure 1), sChematic diagram (figure 2), component location diagram
(figure
3),
and parts lists
(02640-60021
and
02640-60033)
located in
the appendix.
The terminal processor communicates with the Cartridge Tape MOdule via
the terminal bus (Backplane Assembly). The CTU Interface PCA is re-
sponsible for converting processor commands into signals to control
tape motion, unit selection, read or write operation, and the state of
the eject button lights. The CTU Interface peA provides status infor-
mation allowing the processor to determine the present state of the
selected CTU Transport Assembly. Finally, the CIU Interface PCA en-
codes data bytes into serial patterns of bit transitions to be recorded
on the tape and vice versa (i.e., decodes bit transitions on the tape
into data bytes).
3.0.1
BUS FUNCTION DECODE? AND TIMING LOGIC - CTU
IN1~RFACE
PCA.
3.0.1.1
The bus tunction decoder and timing logic generates signals based upon
inputs from the terminal
bUS
which control the flow of commands, sta-
tus, and data bytes to and from the terminal bus.
3.0.1.2
The
bUS
function decoder
(UI6)
generates one ot four command signals
by decoding wRITE and ADUR5. The commands are enabled by I/O (for an
1/0 mOdule), REQ (bus data is valid), ADDR4, AOON11, ADDRtO, and ADDR9.
In addition, DATA CLOCK, RO+WRT, AD/WRT SELECT, READ EN, and STATUS EN
are generated.
3.0.2
COM~AND LOGIC - CTU INTERFACE
peA.
3.0.2.1
The purpose of the command logiC is to acquire command information from
the terminal bus when the signals are valio. The command information
completely specifies the operation as well as the selection of the CTU
Transport Assemblies. In addition, the command logic stops tape motion
thus Dreventing tape runoff when a hole is detected
by
the hole detect
logic.
3.0.2.2
The command signals from the terminal bus are latChed into
U15, U21
(Pins 5 and b), and U24
bv
the CMND CLK signal from the bus function
deCOder and timing loqic.