Cypress FM4 Series - Page 304

CHAPTER 7-3: VBAT Domain(B)
304 FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E
Types of Interface Circuit
There are four types of interface circuit as shown in Table 2-1.
Table 2-1 Types of Interface Circuit
Circuit Type
Always-on
Domain
VBAT
Domain
Transfer Clock
Figure Number
Type 1
FF available
FF unavailable
-
Figure 2-2
Type 2
FF available
FF available
32 kHz
Figure 2-3
Type 3
FF available
FF available
PCLK2 (divided)
Figure 2-4
Type 4
FF unavailable
FF available
-
Figure 2-5
Configuration of
Interface Circuit
Type 4
A signal sent from the Always-on Domain to the VBAT Domain is clipped to the VSS by the level shifter
and the isolator when the Always-on Domain is powered off.
This function enables the following operations to be executed when the Always-on Domain is powered
off: continuing the operation of the calendar function and alarm function of the RTC, holding the pin states
of the VBAT I/O ports, retaining data in the backup registers.
 Interface circuit type 1
Figure 2-2 Configuration of Interface Circuit Type 1
Use this circuit type if the register does not have to retain data when the VCC power supply is off.
Table 2-2 Behavior of Register of Interface Circuit Type 1
Behavior of Register
Initialization of register
Initialization of register by the reset signal of the Always-on Domain
Bus read
The state of the control circuit (Always-on Domain) and that of the peripheral circuit
(VBAT Domain) can be read directly.
Bus write
The register directly affects the operations of the control circuit (Always-on Domain) and
those of the peripheral circuit (VBAT Domain).
Always-on Domain
FF
(Register)
Internal bus
Control
logic
VBAT Domain
Peripheral
function
Level shifter
Isolator