Radio Shack TRS-80 CR-510, Руководство по эксплуатации

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ASCII data. Then, it will read the second card and transmit the ASCII data. The HX3 command (second
string) will cause a command error and the front panel READY lamp will blink (since line two has an
invalid command the PIK that follows HX3 will be ignored). The last PIK command (line 3) will return a
reverse slash in lieu of data (the last card will remain in the hopper). Requesting status and sending a valid
command string will clear the error condition.
Note: an RES command or a DC3 DC4 (13 and 14 HEX) command pair (Hard Reset) will also clear
the error condition. They also reset the Card Reader to its default parameters.
If status had been enabled (ST1), the Card Reader would have transmitted the following:
0,ASCII DATA Carriage Return — Card 1
0,ASCII DATA Carriage Return — Card 2
6,\ Last card remains in the hopper
READY lamp is blinking
A valid command string would clear the error condition.
TRS-80 Microprocessor Input Buffer Management
The XON/XOFF protocol (via 11 HEX and 13 HEX commands to the CR-510) provides an effective
way to control the supply of data to the TRS-80 input buffer.
An XOFF command will cause an immediate interruption in the transmission of data from the Card
Reader to the computer. This command should be used by the TRS-80 to indicate that its buffer
is full (suspend card data transmission).
Note: the XON and XOFF characters are also referred to as DC1 and DC3 on some ASCII tables.
An XON command is the only command that will allow card data transmission to resume once an
XOFF command has been issued. The balance of the data in the CR-510 buffer (remaining card data
interrupted by the XOFF command etc.) will be sent.
Caution: If XOFF is sent during a card read operation with echo enabled, it may be integrated into
the return data string, causing an echo error. If this occurs, an RTX command should be issued
to re-transmit the card data.
Data Transmission Integrity (Echo On)
The return of CR-510 data (from the computer to the CR-510) is an effective method for assuring
data transmission integrity. This is accomplished by turning echo on (EC1 command).
Note: The TRS-80 must echo back the received character (including CR, LF, and Status) before the
Card Reader will transmit the next character.
Every character must be returned to the Card Reader, but only invalid data (not status or carriage
return, etc.) will cause an echo error condition.
If a character is not echoed within 4 seconds, the Card Reader will time-out, initiating an echo error.
The Card Reader will terminate this data transmission with a Carriage Return.
The echo error condition will prevent future card read operations until the error is cleared (as
described below) or until a reset is sent. This provides the TRS-80 with the option of retransmitting
the previous card data (RES or DC3 DC4 flushes the previous card data). An echo error condi-
tion can be cleared by meeting one of the following conditions:
1. TRS-80 computer receives status via: status returned with the card data (ST1), or by requesting
status with an STA command. Then, the computer sends an RTX or PIK command.
2. The Computer sends an RES. The RES will be executed after the current card is read. It will reset
the Card Reader to its default parameters. The CR-510 will be placed in the NOT READY
state. Commands following RES in a string are not lost.
3. The Computer sends a DC3 DC4 command pair. This "hard reset" will be executed immediately (if
a card is halfway through the read head, it will be left there). It will reset the Card Reader to
its default parameters and will be placed in the NOT READY state. All card data in the buffer
will be flushed.