uPD789074 Subseries 8-Bit Single-Chip Microcontrollers UD - Home

CHAPTER 6 16-BIT TIMER 906.4.3 Capture operationThe capture operation consists of latching the count value of 16-bit timer counter 90 (TM90) into a capture registerin synchronization with a capture trigger, and retaining the count value.Set TMC90 as shown in Figure 6-9 to allow 16-bit timer 90 to start the capture operation.Figure 6-9. Settings of 16-Bit Timer Mode Control Register 90 for Capture OperationTOD90 TOF90 CPT901 CPT900 TOC90 TCL901 TCL900 TOE90TMC90− 0/1 0/1 0/1 0/1 0/1 0/1 0/1Count clock selectionCapture edge selection (see Table 6-3)16-bit capture register 90 (TCP90) starts a capture operation after the CPT90 capture trigger edge is detected,and latches and retains the count value of 16-bit timer counter 90. TCP90 fetches the count value within 2 clocks andretains the count value until the next capture edge detection.Table 6-3 and Figure 6-10 show the settings of the capture edge and capture operation timing, respectively.Table 6-3. Settings of Capture EdgeCPT901 CPT900 Capture Edge Selection0 0 Capture operation disabled0 1 CPT90 pin rising edge1 0 CPT90 pin falling edge1 1 CPT90 pin both edgesCaution Because TCP90 is rewritten when a capture trigger edge is detected during a TCP90 read,disable the capture trigger edge detection during a TCP90 read.Figure 6-10. Capture Operation Timing (with Both Edges of CPT90 Pin Specified)Count clockTM900000H0001HNM – 1MCount read buffer0000H0001HNMTCP90UndefinedNMCPT90Capture startCapture edge detectionCapture startCapture edge detectionRemarkN = 0000H to FFFFHM = 0000H to FFFFH92User’s Manual U14801EJ3V1UD