CY545 Stepper System Controller
www.ControlChips.com
Output to Parallel Device
(Including CY233 Network Chip)
The standard parallel output can be used by a parallel connected host or by the CY233 Network
Communications Controller. Both connections use the same signals, the parallel handshake
control lines IO_REQUEST, BUSY, and FPL (USRB6).
When the CY545 receives a Query command or a string to send, it changes to the output mode
internally, and lowers the FPL signal. It then waits for a low level on the IO_REQUEST signal,
indicating that the host or CY233 is ready to take a character.
The character to output is placed on the data bus, and the CY545 drives the BUSY line low,
indicating that a character is available.
The CY545 will now wait in this state until the host or CY233 drives IO_REQUEST high again.
This indicates that the character has been accepted, so the CY545 removes the character from
the data bus, and raises the BUSY line again.
This handshake process repeats until all the characters of the Query output or string have been
sent. The CY545 then drives the FPL line high again, and goes back into the command mode.
A CY233 interface is included with the “CY545 Applications Example”, shown in a previous
chapter.
Output to 8-Digit LED Display
The final selection for a display device is a special parallel display, using the Hewlett-Packard
HDSP-211x displays. These displays are very compact, LED-based, 8 character, dot matrix
displays. They have programmable intensity and custom definable character fonts.
The displays connect to the CY545 over the parallel data bus, the lower address byte, and the
HP_SEL (USRB7) signal. The RD and WR strobes also provide data transfer timing for these
displays.
The applications example schematic includes the proper connections for the HDSP-211x
displays. This connection scheme must be used for proper operation of the displays, because
the CY545 assumes the address lines are connected as shown to access the display control
registers and data buffers.
When the HP display is selected, any string messages are sent to the display verbatim. Be
careful that messages are not longer than 8 characters at a time. Carriage return codes are not
displayed, but they reset the character address to the left most display character, and cause the
display to be blanked before the next character is written.
Query command outputs follow the same format as the standard serial and parallel display
outputs, except for the 8 digit values, which only display the value, so the HP displays can show
one parameter value at a time. The display is blanked, and a new parameter value is written
each time the Query command is used.
© 2002 Cybernetic Micro Systems
52
Chapter 14 - CY545 Output Display Support
ETC [ ETC ]
