AR-B1380/AR-B1380A User’ s Guide
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2.8 PARALLEL PORT
(1) Register Address
Port Address
Read/Write
Register
base + 0
Write
Output data
base + 0
Read
Input data
base + 1
Read
Printer status buffer
base + 2
Write
Printer control latch
Table 2-8 Registers’ Address
(2) Printer Interface Logic
The parallel portion of the SMC37C669 makes the attachment of various devices that accept eight bits of
parallel data at standard TTL level.
(3) Data Swapper
The system microprocessor can read the contents of the printer’ s Data Latch through the Data Swapper by
reading the Data Swapper address.
(4) Printer Status Buffer
The system microprocessor can read the printer status by reading the address of the Printer Status Buffer.
The bit definitions are described as follows:
X
X
X
1
2
3
4
5
6
7
0
-ERROR
SLCT
PE
-ACK
-BUSY
Figure 2-2 Printer Status Buffer
NOTE:
X represents not used.
Bit 7: This signal may become active during data entry, when the printer is off-line during printing, or
when the print head is changing position or in an error state. When Bit 7 is active, the printer is
busy and can not accept data.
Bit 6: This bit represents the current state of the printer’ s ACK signal. A0 means the printer has
received the character and is ready to accept another. Normally, this signal will be active for
approximately 5 microseconds before receiving a BUSY message stops.
Bit 5: A1 means the printer has detected the end of the paper.
Bit 4: A1 means the printer is selected.
Bit 3: A0 means the printer has encountered an error condition.
(5) Printer Control Latch & Printer Control Swapper
The system microprocessor can read the contents of the printer control latch by reading the address of
printer control swapper. Bit definitions are as follows:
Summary of Contents for AR-B1380
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