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7.2.2 Data communication with intelligent function modules
Data is transmitted or received in 16-bit or 32-bit units. Intelligent function modules
have a buffer memory to store those data.
QCPU
Buffer
memory
Reading data
Writing data
Data
Intelligent function module
0
1
2
10
Buffer memory address
Readable and
writable by QCPU
Example of memory map: Q62DAN D/A converter module
D/A conversion enable/disable
CH1 Digital value
CH2 Digital value
CH1 Set value check code
CH2 Set value check code
3
t
o
11
12
System area (use prohibited)
Figure 7.5 Buffer memory
(1) QCPUs can read and write data to and from the buffer memory. Also note that
some modules can write data to buffer memory from peripheral device via an
interface.
(2) In a buffer memory, space of one word (16 bits) is reserved for each intelligent
function module's unique address.
The smallest address is 0, and these addresses are used to specify a target
module to read or write. The minimum unit is one word. Data of 17 bits to 32
bits is treated as 2-word (32-bit) data.
0 00100010100
B15
B14
B13
B12 B11
B10B9B8B7B6B5B4B3B2B1B0
Data part
Sign bit
1: Negative
0: Positive
Indicated here is +276.
(Negative digital values are represented
in two's complement.)
Figure 7.6 Example image of buffer memory content (D/A converter module)
Figure 7.6 shows 16 bits of the buffer memory of a D/A converter module where
a digital quantities have been written. The number is obtained from digital
quantity that a QCPU wrote to the buffer memory within the range from -4096 to
+4095 in signed binary (16 bits long).
(3) A buffer memory is a RAM.