SCDS149B October 2003 – December 2025 SN74CB3T3257
PRODUCTION DATA
The 4-bit bus is connected directly to the 1A, 2A, 3A, and 4A ports (known as the xA port) on the SN74CB3T3257. This splits into two buses, out of the xB1 and xB2 ports. When S is high, xB2 is the active bus, and when S is low, xB1 is the active bus. This means that Device 2 is connected to the bus controller when S is high, and Device 1 is connected to the bus controller when S is low. This setup is useful when two devices are hard coded with the same address and only one bus is available. The OE connection can be used to disconnect all devices from the bus controller if necessary.
The 0.1µF capacitor on VCC is a decoupling capacitor and must be placed as close as possible to the device.