– 24 –2-1-2. RS-422A InterfaceFig. 2-3 RS-422A InterfaceData flow from host to printer passes from the RD terminal to the IC1 on the interface board and is input to the CPU.The IC1 converts the RS-422A and TTL voltage levels.The CPU converts the input serial data to parallel data and stores that data in the memory buffer memory. It also convertsthe internal parallel data to serial data and outputs that to the IC1.D2O
D1O
D2EN
D2I
D1EN
D1I
ERROR
ACK
RD (+)
RD (
-
)
CS (+)
CS (
-
)
RS (
-
)
RS (+)
SD (
-
)
SD (+)
CN3 CN1
IC1
+
-
+
-
Gate
Array
CN9 IC10
R2I
+
R2I
-
R1I
+
R1I
-
D2O
D2O
D1O
D1O
RXD0
TXD0
RXD1
CPU
IC5
A15
B15
A10
B12
B14
A15
B15
A10
B12
B14
MC34051