Epson TM-T88IV TM-T88IV Technical Reference Guide - Page 86

IEEE 1284 Parallel Interface, Modes

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IEEE 1284 Parallel Interface Modes The IEEE 1284 parallel interface supports the following two modes. Mode Communication direction Other information Compatibility mode Host → Printer communication Centronics-compliant Reverse mode Printer → Host communication Assumes a data transfer from an asynchronous printer Compatibility Mode Compatibility mode allows data transmission from host to printer only: Centronics-compatible. Specification Data transmission 8-bit parallel Synchronization Externally supplied STROBE signals Handshaking ACK and BUSY signals Signal levels TTL-compatible connector Connector ADS-B36BLFDR176 (HONDA) or equivalent product Reverse communication Nibble or byte mode Reverse Mode The transfer of status data from the printer to the host proceeds in the nibble or byte mode. This mode allows data transfer from an asynchronous printer under the control of the host. Data transfers in the nibble mode are made via the existing control lines in units of four bits (a nibble). In the byte mode, data transfer proceeds by making the 8-bit data lines bidirectional. Both modes fail to proceed concurrently in the compatibility mode, thereby causing half-duplex transmission. 86

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86
IEEE 1284 Parallel Interface
Modes
The IEEE 1284 parallel
int
erface s
u
ppor
t
s
t
he follow
ing
t
wo modes.
Compatibility Mode
Compa
ti
b
i
l
it
y mode allows da
t
a
t
ra
n
sm
i
ss
i
o
n
from hos
t
t
o pr
int
er o
n
ly: Ce
nt
ro
ni
cs-compa
ti
ble.
Specification
Reverse Mode
The
t
ra
n
sfer of s
t
a
tu
s da
t
a from
t
he pr
int
er
t
o
t
he hos
t
proceeds
in
t
he
ni
bble or by
t
e mode.
Th
i
s mode allows da
t
a
t
ra
n
sfer from a
n
asy
n
chro
n
o
u
s pr
int
er
un
der
t
he co
nt
rol of
t
he hos
t
. Da
t
a
t
ra
n
sfers
in
t
he
ni
bble mode are made v
i
a
t
he ex
i
s
ting
co
nt
rol l
in
es
in
unit
s of fo
u
r b
it
s (a
ni
bble).
I
n
t
he by
t
e mode, da
t
a
t
ra
n
sfer proceeds by mak
ing
t
he 8-b
it
da
t
a l
in
es b
i
d
i
rec
ti
o
n
al. Bo
t
h modes
fa
i
l
t
o proceed co
n
c
u
rre
nt
ly
in
t
he compa
ti
b
i
l
it
y mode,
t
hereby ca
u
s
ing
half-d
u
plex
t
ra
n
sm
i
ss
i
o
n
.
Mode
Communication direction
Other information
Compatibility mode
Host
→
Printer communication
Centronics-compliant
Reverse mode
Printer
→
Host communication
Assumes a data transfer from an
asynchronous printer
Data transmission
8-bit parallel
Synchronization
Externally supplied STROBE
signals
Handshaking
ACK
and BUSY signals
Signal levels
TTL-compatible connector
Connector
ADS-B36BLFDR176 (HONDA) or equivalent product
Reverse communication
Nibble or byte mode