Freescale Semiconductor SC140 Comparator B Condition Selection, Comparator a Condition Selection

Event Detection Unit (EDU) Channels and Registers

Table 4-19. EDCA_CTRL Description (Continued)

Name	Description	Settings
CBCS	Comparator B Condition Selection —	00	= Equal to EDCA_REFB
Bits 7–6	Used to select one of these four results	01	= Not equal to EDCA_REFB
	from comparator B:	10	= Greater than EDCA_REFB
	• Equal to	11	= Less than EDCA_REFB
	• Not equal to
	• Greater than
	• Less than
CACS	Comparator A Condition Selection —	00	= Equal to EDCA_REFA
Bits 5–4	Used to select one of these four results	01	= Not equal to EDCA_REFA
	from comparator A:	10	= Greater than EDCA_REFA
	• Equal to	11	= Less than EDCA_REFA
	• Not equal to
	• Greater than
	• Less than
ATS	Access Type Selection — These bits	00	= Read access
Bits 3–2	are used to select the type of memory	01	= Write access
	access that should be detected by the	10	= Read or write access
	event detection channel. The possible	11	= Reserved
	memory access types are:
	• Read access
	• Write access
	• Read or write access
BS	Bus Selection — Used to select which	00	= XABA
Bits 1–0	address bus or buses should be	01	= XABB
	sampled for comparison by comparator	10	= XABA and XABB
	A and/or by comparator B. The possible	11	= PC
	buses that can be chosen by these bits
	are PC, XABA, and XABB.
	If XABA and/or XABB are the selected
	buses, bus XABA is compared to the
	EDCA_REFA register while XABB is
	compared to the EDCA_REFB register.
	If CS bits are set to 11, then setting BS
	bits to 10 enables the user to set a
	watchpoint on an address when it is not
	known whether the address to be used
	for accessing memory is on XABA or
	XABB. In this case, the user must set
	both reference value registers with the
	address to be detected.
	If the BS bits are set to 10, then the CS
	bits must be set to either 10 or 11.

In order to detect a watchpoint on a PC range, one EDCA is enough. In order to detect a watchpoint on a data address range, two EDCAs are required. When configuring two EDCAs to detect a watchpoint to an address range, one EDCA should be configured to detect the range on bus A, and the other EDCA to detect

4-56 SC140 DSP Core Reference Manual