IBM 5280 Technical Newsletter page 19

Page of SY31-Q600-1
As updated January 30, 1981
By TN L SN20-9543
When a card is inserted into the magnetic stripe reader,
the data is amplified, sent to the adapter, and stored in
the adapter buffer. When the data is in the buffer, the
adapter issues a service request to the keyboard/display
MPU and waits for the MPU to service the request.
When the MPU detects that an MSR is waiting for service,
the MPU determines which MSR is requesting service and
reads a byte of data from the adapter buffer. After the
MPU has processed the data, it reads another byte of
data, and so on, until all the data has been read. When
the final byte of data has been read, the adapter is reset
to allow the reader to accept another card.
Refer to logic diagram LDOB. LD09 shows the logic for
the MSR adapter. The keyboard/display MPU controls
the adapter by sending commands on the '-EAR bit 0 dot'
through '-EAR bit 7 dot' lines. The MPU reads data from
the MSR on the '-100 in bit 0 dot' through '-100 in bit
7 dot' lines.
258
ELAPSED TIME COUNTER
The elapsed time counter is used to determine elapsed real
time. The counter is attached to the keyboard/display
MPU through an MPU I/O register.
The MPU reads the time and places it in the system control
area in main storage. The counter is increased in incre-
ments of 1.6 seconds. An application program reads the
time and calculates elapsed time.
Refer to diagram LD09. LD09 shows the logic for the
elapsed time counter. The keyboard/display MPU
controls the counter by sending commands on the
'-EAR bit 0 dot' through '-EAR bit 7 dot' lines. The
MPU reads the counter data on the '100 in bit 4 dot'
through '-100 in bit 7 dot' lines.
BUFFER TIMER
The buffer timer provides a timeout to the key-
board/display MPU. If the main MPU has not serviced the
keyboard before the timeout occurs, the keyboard/display
MPU reads the buffer for a command key sequence. If a
command key sequence has occurred, the keyboard/display
MPU moves the scan code for the key to the
keyboard/displa~
lOB and signals the main MPU. If a command key sequence
has not occurred, a keyboard overrun condition occurs.