abaco systems CEI-520 - CSDB Transmit Data Format; Table 44. CSDB Transmit Buffer; Table 45. Typical CSDB Message Lengths

Program Interface Library AR_PUTWORD
CEI-100/CEI-200/CEI-x20 User’s Manual 123
The firmware reads 16-bits from dual-port RAM, zero extended
(enhanced API) or 32-bits (standard API), and outputs the entire value to
the FPGA, even through only the lower 12 bits contain useful data. The
host is responsible for loading the transmit buffer with data at a rate
such that the buffer never becomes empty, and must place the sync
words in the data stream at the proper places, if a proper 573/717 data
stream is to be maintained. The ENHANCED API provides a transmit
mode for 573/717 channels called FRAME mode. In this mode the
transmit buffer is filled by the host, and then the firmware cycles
through the data, transmitting each word in turn. When the end of the
buffer is reached the firmware returns to the beginning and transmits
the data again and again. The AR_PUTBLOCK function can be used to
update sections or the entire transmit buffer.
CSDB Transmit Data Format
For board channels configured as CSDB, the transmit word must be
formatted by the application as follows:
Table 44. CSDB Transmit Buffer
31 - 16
15
14
13 – 8
7 - 0
Transmit length
(message length - 1
in bits)
PARITY ENABLE
0=disabled
1=enabled
(when enabled, the parity of
the eight bit data word is
calculated and the parity bit is
added to the transmission)
PARITY
SELECT
0=odd
1=even
Not
used
DATA
8 bit data word
Transmit length is a value one less than the overall length of the CSDB
message. All transmitted words contain at least a start-bit, eight data-bits,
a parity-bit (if enabled) and a stop-bit, regardless of the value of Transmit
length. This field is useful for controlling the number of stop-bits in a
continuous transmission. It is also useful for programming gaps of stop-
bits for transmit scheduling. Typical Transmit length values are shown in
the following table:
Table 45. Typical CSDB Message Lengths
N-1
Start
Data Bits
Parity
Stop Bits
10
1
8
1
1
11
1
8
1
2
9
1
8
0
1
10
1
8
0
2
Note:
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