CYW20702
3.9 Serial Enhanced Coexistence Interface
The Serial Enhanced Coexistence Interface (Serial ECI or SECI) is a proprietary Cypress interface between Cypress WLAN devices
and Bluetooth devices. It is an optional replacement to the legacy 3- or 4-wire coexistence feature, which is also available.
The following key features are associated with the interface:
■ Enhanced coexistence data can be exchanged over a two-wire interface, one serial input (SECI_IN), and one serial output
(SECI_OUT). The pad configuration registers must be programmed to choose the digital I/O pins that serve the SECI_IN and
SECI_OUT function.
■ It supports generic UART communication between WLAN and Bluetooth devices.
■ To conserve power, it is disabled when inactive.
■ It supports automatic resynchronizaton upon waking from sleep mode.
■ It supports a baud rate of up to 4 Mbps.
3.9.1 SECI Advantages
The advantages of the SECI over the legacy 3-wire coexistence interface are:
■ Only two wires are required: SECI_IN and SECI_OUT.
■ Up to 48-bits of coexistence data can be exchanged.
Previous Cypress standalone Bluetooth devices such as the BCM2070 supported only a 3-wire or 4-wire coexistence interface.
Previous Cypress WLAN and Bluetooth combination devices such as the CYW4325, CYW4329, and CYW4330 support an internal
parallel enhanced coexistence interface for more efficient WLAN and Bluetooth information exchange. The SECI allows enhanced
coexistence information to be passed to a companion Cypress WLAN chip through a serial interface using fewer I/O than the 3-wire
coexistence scheme.
The 48-bits of the SECI significantly enhance WLAN and Bluetooth coexistence by sharing such information as frequencies used and
radio usage times. The exact contents of the SECI are Cypress confidential.
3.9.2 SECI I/O
The CYW20702 does not have dedicated SECI_IN or SECI_OUT pins, but the two pin functions can be mapped to the following digital
I/O: the UART, GPIO, SPI Master (or BSC), PCM, and COEX pins. Pin function mapping is controlled by the config file that is either
stored in NVRAM or downloaded directly into on-chip RAM from the host.
Document Number: 002-14773 Rev. *L
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