Visible to Intel only — GUID: iga1405469061453
Ixiasoft
Visible to Intel only — GUID: iga1405469061453
Ixiasoft
11.4.3.2. txdata Register
Avalon® -MM host peripherals write characters to be transmitted into the txdata register. Characters should not be written to txdata until the transmitter is ready for a new character, as indicated by the TRDY bit in the status register. The TRDY bit is set to 0 when a character is written into the txdata register. The TRDY bit is set to 1 when the character is transferred from the txdata register into the transmitter shift register. If a character is written to the txdata register when TRDY is 0, the result is undefined. Reading the txdata register returns an undefined value.
For example, assume the transmitter logic is idle and an Avalon® -MM host peripheral writes a first character into the txdata register. The TRDY bit is set to 0, then set to 1 when the character is transferred into the transmitter shift register. The host can then write a second character into the txdata register, and the TRDY bit is set to 0 again. However, this time the shift register is still busy shifting out the first character to the TXD output. The TRDY bit is not set to 1 until the first character is fully shifted out and the second character is automatically transferred into the transmitter shift register.