Motorola MCF5282 IST10 Input Sample Times, Non-Multiplexed Input Signals Channel Number

Register Descriptions

		Table 27-14. CCW Field Descriptions (continued)
Bit(s)	Name		Description
7–6	IST		Input sample time. Specifies the length of the sample window. The input sample time can be
			varied, under software control, to accommodate various input channel source impedances.
			Longer sample times permit more accurate A/D conversions of signals with higher source
			impedances.
			Table 27-15shows the four selectable input sample times.
			The programmable sample time can also be used to adjust queue execution time or sampling
			rate by increasing the time interval between conversions.
5–0	CHAN		Selects the input channel number. The CCW channel field is programmed with the channel
			number corresponding to the analog input signal to be sampled and converted. The analog input
			signal channel number assignments and the signal definitions vary depending on whether the
			QADC multiplexed or non-multiplexed mode is used by the application. As far as queue
			scanning operations are concerned, there is no distinction between an internally or externally
			multiplexed analog input.
			Table 27-16shows the channel number assignments for non-multiplexed mode. Table 27-17
			shows the channel number assignments for multiplexed mode.
			Programming the channel field to channel 63 denotes the end of the queue. Channels 60 to 62
			are special internal channels. When one of the special channels is selected, the sampling
			amplifier is not used. The value of VRL, VRH, or (VRH–VRL)/2 is converted directly.
			Programming any input sample time other than two has no benefit for the special internal
			channels except to lengthen the overall conversion time.

	Table 27-15. Input Sample Times
IST[1:0]	Input Sample Times

00Input sample time = QCLK period ⋅ 2

01Input sample time = QCLK period ⋅ 4

10Input sample time = QCLK period ⋅ 8

11Input sample time = QCLK period ⋅ 16

Table 27-16. Non-Multiplexed Channel Assignments and Signal Designations

	Non-Multiplexed Input Signals			Channel Number 1
				in CCW CHAN Field
Port Signal Name	Analog Signal Name	Other	Signal Type	Binary	Decimal
		Functions
PQB0	AN0	—	Input	000000	0
PQB1	AN1	—	Input	000001	1
PQB2	AN2	—	Input	000010	2
PQB3	AN3	—	Input	000011	3
PQA0	AN52	—	Input/Output	110100	52
PQA1	AN53	—	Input/Output	110101	53
PQA3	AN55	ETRIG1	Input/Output	110111	55
PQA4	AN56	ETRIG2	Input/Output	111000	56
V	Low reference	—	Input	111100	60
VRL	High reference	—	Input	111101	61
RH	—	(VRH–VRL)/2	—	111110	62
—
—	—	End-of-Queue Code	—	111111	63

1All channels not listed are reserved or unimplemented and return undefined results.

27-28 MCF5282 User’s Manual MOTOROLA