Intel 8XC251SQ, 8XC251SA, 8XC251SP, 8XC251SB PCA Software Timer and High-speed Output Modes

8XC251SA, SB, SP, SQ USER’S MANUAL

Count

Input

PCA Timer/Counter

CH	CL
(8 Bits)	(8 Bits)

Compare/Capture

Module

CCAPxH CCAPxL (8 Bits) (8 Bits)

						Toggle
		16-Bit		Match			CEXx
		Comparator
							Interrupt
	Enable					CCFx	Request
						CCON	Enable
X	ECOMx	0	0	MATx	TOGx	0	ECCFx
7		CCAPMx Mode Register					0
"0"

Reset

Write to CCAPxL

"1" Write to CCAPx H

X= Don't Care x = 0, 1, 2, 3, 4

For software timer mode, set ECOMx and MATx.

For high speed output mode, set ECOMx, MATx, and TOGx.

A4164-01

Figure 9-3. PCA Software Timer and High-speed Output Modes

9.3.4High-speed Output Mode

The high-speed output mode (Figure 9-3) generates an output signal by toggling the module’s I/O pin (CEXx) when a match occurs. This provides greater accuracy than toggling pins in software because the toggle occurs before the interrupt request is serviced. Thus, interrupt response time does not affect the accuracy of the output.

To program a compare/capture module for the high-speed output mode, set the ECOMx, MATx, TOGx bits in the module’s CCAPM x register. Table 9-3 on page 9-14 lists the bit combinations for selecting module modes. A match between the PCA timer/counter and the compare/capture registers (CCAPxH/CCAPxL) toggles the CEXx pin and sets the module’s compare/capture flag (CCFx in the CCON register). By setting or clearing the CEXx pin in software, the user selects whether the match toggles the pin from low to high or vice versa.

9-8