27.5.1 Control A
| Name: | CTRLA |
| Offset: | 0x00 |
| Reset: | 0x00 |
| Property: | - |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| SDASETUP | SDAHOLD[1:0] | FMPEN | |||||||
| Access | R/W | R/W | R/W | R/W | |||||
| Reset | 0 | 0 | 0 | 0 | |||||
Bit 4 – SDASETUP SDA Setup Time
By default, there are four clock cycles of setup time on SDA out signal while reading from the slave part of the TWI module. Writing this bit to '1' will change the setup time to eight clocks.
| Value | Name | Description |
|---|---|---|
| 0 | 4CYC | SDA setup time is four clock cycles |
| 1 | 8CYC | SDA setup time is eight clock cycle |
Bits 3:2 – SDAHOLD[1:0] SDA Hold Time
Writing these bits selects the SDA hold time.
| SDAHOLD[1:0] | Nominal Hold Time | Hold Time Range Across All Corners (ns) | Description |
|---|---|---|---|
| 0x0 | OFF | 0 | Hold time off. |
| 0x1 | 50 ns | 36 - 131 | Backward compatible setting. |
| 0x2 | 300 ns | 180 - 630 | Meets SMBus specification under typical conditions. |
| 0x3 | 500 ns | 300 - 1050 | Meets SMBus specification across all corners. |
Bit 1 – FMPEN FM Plus Enable
Writing these bits selects the 1 MHz bus speed (Fast mode plus, Fm+) for the TWI in default configuration.
| Value | Description |
|---|---|
| 0 | Fm+ disabled |
| 1 | Fm+ enabled |