参数资料
型号: M34518E8SP
元件分类: 微控制器/微处理器
英文描述: 4-BIT, OTPROM, 6 MHz, MICROCONTROLLER, PDIP32
封装: 8.90 X 28 MM, 1.78 MM PITCH, PLASTIC, SDIP-32
文件页数: 112/162页
文件大小: 1149K
代理商: M34518E8SP
Rev.3.01
2005.06.15
page 51 of 157
REJ03B0008-0301
4518 Group
(9) Operation at comparator mode
The A/D converter is set to comparator mode by setting bit 3 of the
register Q1 to “1.”
Below, the operation at comparator mode is described.
(10) Comparator register
In comparator mode, the built-in DA comparator is connected to the
8-bit comparator register as a register for setting comparison volt-
ages. The contents of register B is stored in the high-order 4 bits of
the comparator register and the contents of register A is stored in
the low-order 4 bits of the comparator register with the TADAB in-
struction.
When changing from A/D conversion mode to comparator mode,
the result of A/D conversion (register AD) is undefined.
However, because the comparator register is separated from regis-
ter AD, the value is retained even when changing from comparator
mode to A/D conversion mode. Note that the comparator register
can be written and read at only comparator mode.
If the value in the comparator register is n, the logic value of com-
parison voltage Vref generated by the built-in DA converter can be
determined from the following formula:
(11) Comparison result store flag (ADF)
In comparator mode, the ADF flag, which shows completion of A/D
conversion, stores the results of comparing the analog input volt-
age with the comparison voltage. When the analog input voltage is
lower than the comparison voltage, the ADF flag is set to “1.” The
state of ADF flag can be examined with the skip instruction
(SNZAD). Use the interrupt control register V2 to select the inter-
rupt or the skip instruction.
The ADF flag is cleared to “0” when the interrupt occurs or when
the next instruction is skipped with the skip instruction.
(12) Comparator operation start instruction
(ADST instruction)
In comparator mode, executing ADST starts the comparator oper-
ating.
The comparator stops 2 machine cycles + A/D conversion clock
f(ADCK) 1 clock after it has started (4
s at f(XIN) = 6.0 MHz in XIN
through mode, f(ADCK) = f(INSTCK)/6). When the analog input
voltage is lower than the comparison voltage, the ADF flag is set to
“1.”
(13) Notes for the use of A/D conversion
TALA instruction
When the TALA instruction is executed, the low-order 2 bits of
register AD is transferred to the high-order 2 bits of register A, si-
multaneously, the low-order 2 bits of register A is “0.”
Operation mode of A/D converter
Do not change the operating mode (both A/D conversion mode
and comparator mode) of A/D converter with the bit 3 of register
Q1 while the A/D converter is operating.
Clear the bit 2 of register V2 to “0” to change the operating mode
of the A/D converter from the comparator mode to A/D conver-
sion mode.
The A/D conversion completion flag (ADF) may be set when the
operating mode of the A/D converter is changed from the com-
parator mode to the A/D conversion mode. Accordingly, set a
value to the register Q1, and execute the SNZAD instruction to
clear the ADF flag.
Logic value of comparison voltage Vref
Vref =
n
n: The value of register AD (n = 0 to 255)
Fig. 40 Comparator operation timing chart
VDD
256
ADST instruction
Comparison result
store flag(ADF)
2 machine cycles + 1/f(ADCK)
DAC operation signal
Comparator operation completed.
(The value of ADF is determined)
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