SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
The EQEP peripheral includes a position-compare unit that is used to generate a sync output and/or interrupt on a position-compare match. Figure 12-2700 shows a diagram. The position-compare (EQEP_QPOSCMP) register is shadowed and shadow mode can be enabled or disabled using the EQEP_QCAP_QPOS_CTL[31] PCSHDW bit. If the shadow mode is not enabled, the CPU writes directly to the active position compare register.
In shadow mode, SW can configure the position-compare unit (EQEP_QCAP_QPOS_CTL[30] PCLOAD) to load the shadow register value into the active register on the following events and to generate the position-compare ready (EQEP_QINT_EN_FLG[23] PCRI_FLG) interrupt after loading.
The position-compare match (EQEP_QINT_EN_FLG[24] PCMI_FLG) is set when the position-counter value (QPOSCNT) matches with the active position-compare register (EQEP_QPOSCMP) and the position-compare sync output of the programmable pulse width is generated on compare match to trigger an external device.
For example, if EQEP_QPOSCMP bitfield POSCMP = 0x2, the position-compare unit generates a position-compare event on the transition from 1 to 2 of the EQEP position counter for forward counting direction and on the transition from 3 to 2 of the EQEP position counter for reverse counting direction (see Figure 12-2701).
When EQEP_QCAP_QPOS_CTL[30] PCLOAD=0h, the shadow register is loaded into the active register as soon as POSCNT becomes zero, and it should not generate another shadow load if the POSCNT continues to stay at zero
The pulse stretcher logic in the position-compare unit generates a programmable position-compare sync pulse output on the position-compare match. In the event of a new position-compare match while a previous position-compare pulse is still active, then the pulse stretcher generates a pulse of specified duration from the new position-compare event as shown in Figure 12-2702.