32. 12-Bit A/D Converter (S12AD)
Under development Preliminary document
Specifications in this document are tentative and subject to change.
32.3.5
Analog Input Sampling and Scan Conversion Time
Scan conversion can be activated either by software trigger; the triggers from the MTU, ELC, or temperature sensor; or
ADTRG0# (external trigger). After start-of-scanning-delay time (tD) has passed, the A/D converter samples the channel-
dedicated sample-and-hold circuits, executes the disconnection detection assist process, the conversion process for self-
diagnosis, and then starts the A/D conversion process.
Figure 32.16 shows the scan conversion timing in single-cycle scan mode, in which scan conversion is activated by
software trigger or triggers from the MTU, ELC, or temperature sensor.
Figure 32.17 shows the scan conversion timing
in single-cycle scan mode, in which scan conversion is activated by ADTRG0# (external trigger). The scan conversion
time (tSCAN) includes start-of-scanning-delay time (tD), channel-dedicated sample-and-hold circuits sampling time
(tSH)*1, disconnection detection assist processing time (tDIS)*2, self-diagnosis A/D conversion processing time
(tDIAG)*3, A/D conversion processing time (tCONV), channel-dedicated sample-and-hold circuit sampling-and-holding
end time (tSHED)*4, and end-of-scanning-delay time (tED). Table 32.9 shows the specific scanning time. The scan conversion time (tSCAN) in single-cycle scan mode for which the number of selected channels is n can be
determined as follows:
tSCAN = tD + tSH + (tDIS× n) + tDIAG + (tCONV × n) + tED
The scan conversion time for the first cycle in continuous scan mode is tSCAN for single-cycle scan minus tED plus tSHED.
The scan conversion time for the second and subsequent cycles in continuous scan mode is fixed to tSH + (tDIS× n) +
tDIAG + (tCONV × n) + tSHED.
The disconnection detection assist processing time (tDIS) is the value set in the ADNDIS[3:0] bits.
The channel-dedicated sample-and-hold circuits sampling time (tSH) is 10 states (fixed) + the value set in the
ADSHCR.SSTSH[7:0] bits.
The self-diagnosis A/D conversion processing time (tDIAG) is 30 states (fixed) + the value set in the
ADSSTR0.SST00[7:0] bits.
The A/D conversion processing time (tCONV) is 30 states (fixed) + the value set in the ADSSTn.SSTxx[7:0] bits*5.
Note 1.
When no channel-dedicated sample-and-hold circuits are used, tSH = 0.
Note 2.
When the disconnection detection assist function is not used, tDIS = 0.
Note 3.
When the self-diagnosis function is not used, tDIAG = 0.
Note 4.
When no channel-dedicated sample-and-hold circuits are used, tSHED = 0. Here, continuous scan mode is
assumed. In single-cycle scan mode and group scan mode, tSHED is included in the end-of-scanning-delay time
(tED).
Note 5.