This document introduces Cypress low-speed and full-speed M8 USB devices and provides a complete USB to serial bridge solution for replacing traditional RS-232 serial interfaces.
The document presents a reference design that enables peripheral manufacturers to replace legacy RS‑232 interfaces with USB without changing existing PC application software. It outlines a staged migration path, a Windows driver that creates a virtual COM port, and firmware for the CY7C637xx low‑speed and CY7C640/1xx full‑speed USB microcontroller families.
The design details include driver capabilities, supported baud rates and flow‑control signals, firmware architecture, endpoint data flow, and configuration of serial port parameters via HID feature reports. Limitations such as half‑duplex operation and default baud‑rate range are also discussed, with guidance on customizing the firmware for higher performance.
| Supported Windows operating systems | Windows 98, Windows Me, Windows 2000, Windows XP |
|---|---|
| Data throughput | >4000 bytes/s (full‑speed) / 800 bytes/s (low‑speed) |
| Supported word lengths | 5, 6, 7, 8 bytes |
| Supported flow‑control signals | RTS, CTS, DRT, DSR, RI, CD |
The driver works with Windows 98, Windows Me, Windows 2000 and Windows XP.
It can sustain more than 4000 bytes per second.
Yes, by customizing the firmware the baud rate can be increased up to 192 kbaud.