Rev 1.1 | SC5520A & SC5521A
Hardware Manual
SignalCore, Inc.
36
Figure 6. Query example: Write followed by Read to the GET_SERIAL_BUFFER
In the figure above, the first transfer cycle is to make the request for list start frequency data through the
GET_DEVICE_PARAM register. The subsequent cycle is to clock the data that was requested by sending 64
clocks into the GET_SERIAL_BUFFER register.
RS232 Interface
The RS232 version of the SC5521A has a standard interface buffered by an RS232 transceiver so that it
may interface directly with many host devices, such as a desktop computer. The interface connector for
RS232 communication is labeled “Digital I/O” on the front of the panel. Refer
out information. The RS232 device communication control set is provided in the following table.
Table 8. RS232 Control Setting
Baud rate Rate of transmission
*Pin 16 of the Digital IO connector selects the rate. By default, if the pin is pulled high or open, the rate is
set to 115200 at power up or upon HW reset. When the pin is pulled low or grounded, the rate is set to
57600 upon reset or power up.
Data bits The number of bits in the data is fixed at 8.
Parity Parity is 0 (zero)
Stop bits 1 stop bit
Flow control 0 (zero) or none
Only 3-wire RS232 is required since hardware flow control is not used. These connections are the Tx, Rx,
and Gnd. This interface is common on most host computers and microcontrollers, so user access to host
ports is readily provided by the computer OS or microcontroller hardware registers.
Writing to the Device Via RS232
It is important that all necessary bytes associated with any one register are fully sent. In other words, if a
register requires a total of 6 bytes (address plus data), then all 6 bytes must be sent even though the last
byte may be null. The device, upon receiving the first register addressing byte, will wait for all the
associated data bytes before acting on the register instruction. Failure to complete the register
