![](http://datasheet.mmic.net.cn/370000/UPD75236GJ_datasheet_16740772/UPD75236GJ_116.png)
116
μ
PD75236
(4)
SA register (SA)
The SA register (Successive Approximation Register) is an 8-bit register to store the result of A/D
conversion by successive approximation.
The SA register is read by an 8-bit manipulation instruction. Data cannot be written to this register by
software.
RESET input sets the SA register to 7FH.
(5)
A/D converter operations
The analog input signal to undergo A/D conversion is specified by setting bits 6, 5 and 4 (ADM6, 5 and
4) of the A/D conversion mode register.
A/D conversion is started by setting (1) ADM bit 3 (SOC). SOC is automatically cleared (0) after the
setting. A/D conversion is executed using successive approximation by hardware and the 8-bit conversion
result data is stored into the SA register. Upon termination of conversion, bit 2 (EOC) of ADM is set (1).
Fig. 4-64 is an A/D conversion timing chart.
Use the A/D converter as follows.
Select the analog input channel (ADM 6, 5 and 4 setting).
Instruct A/D conversion start (SOC setting).
Wait for A/D conversion to terminate (wait for EOC to be set or wait with a software timer).
Read the A/D conversion result (SA register reading).
4
Note
1.
and
can be carried out simultaneously.
2. A maximum delay of 2
4
/f
X
sec (3.81
μ
s: at 4.19 MHz operation) occurs from A/D conversion start to
EOC clear after SOC setting. Thus, test EOC after the passage of time indicated in Table 4-11 after
SOC setting. Table 4-7 shows A/D conversion times as well.
Table 4-7 SCC and PCC Settings
SCC and PCC Set Value
A/D Conversion
Time
Wait not required
2 machine cycles
4 machine cycles
Wait not required
Wait time till EOC
test after SOC
setting
Wait time till the
end of A/D conver-
sion after SOC
setting
3 machine cycles
21 machine cycles
42 machine cycles
Wait not required
Conversion
operation
stopped
—
—
168/f
x
(40.1
μ
s : at 4.19
MHz operation)
Remarks
x : Don’t care
SCC3
SCC0
PCC1
PCC0
0
0
0
0
1
0
1
1
0
1
×
×
1
×
×
×