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UG-1262
Rev. B | Page 235 of 312
SERIAL CLOCK PERIOD DIVISOR REGISTER
Address: 0x40003024, Reset: 0x1F1F, Name: DIV
Table 291. Bit Descriptions for DIV
Bits Bit
Name Settings Description
Reset Access
[15:8] HIGH
Serial Clock High Time. This register controls the clock high time. The PCLK drives the timer.
To derive the required high time, calculate: High = (REQD_HIGH_TIME/PCLK_PERIOD) – 2.
For example, to generate a 400 kHz I2C_SCL with a low time of 1300 ns and a high time of
1200 ns, with a core clock frequency of 26 MHz, Low = 1300 ns/38 ns − 1 = 0x21 (33
decimal). High = 1200 ns/38 ns − 2 = 0x1D (29 decimal). This register is reset to 0x1F,
which gives an I2C_SCL high time of 33 PCLK cycles.
0x1F R/W
[7:0] LOW
Serial Clock Low Time. This register controls the clock low time. The PCLK drives the timer.
To derive the required low time, calculate: Low = (REQD_LOW_TIME/PCLK_PERIOD) – 1.
This register is reset to 0x1F, which gives an I2C_SCL low time of 32 PCLK cycles.
0x1F R/W
SLAVE CONTROL REGISTER
Address: 0x40003028, Reset: 0x0000, Name: SCTL
Table 292. Bit Descriptions for SCTL
Bits Bit
Name Settings Description
Reset Access
15 Reserved
Reserved.
0x0 R
14
STXDMA
Enable Slave Transmit DMA Request.
0x0
R/W
0
Disable DMA mode.
1
Enable
I
2
C slave DMA receive requests.
13
SRXDMA
Enable Slave Receive DMA Request.
0x0
R/W
0
Disable DMA mode.
1
Enable
I
2
C slave DMA receive requests.
12
IENREPST
Repeated Start Interrupt Enable.
0x0
R/W
0
Interrupt not generated when the SSTAT, Bit 13 asserts.
1
Generate interrupt when the SSTAT, Bit 13 asserts.
11 Reserved
Reserved.
0x0 R/W
10
IENSTX
Slave Transmit Request Interrupt Enable.
0x0
R/W
9
IENSRX
Slave Receive Request Interrupt Enable.
0x0
R/W
8
IENSTOP
Stop Condition Detected Interrupt Enable.
0x0
R/W
7 NACK
No Acknowledge Next Communication. If this bit is set, the next communication is not
acknowledged.
0x0 R/W
6
Reserved
Reserved. Write 0 to this bit.
0x0
R/W
5 EARLYTXR
Early Transmit Request Mode. Setting this bit enables a transmit request immediately
after the positive edge of the direction bit I2C_SCL clock pulse.
0x0 R/W
4
GCSBCLR
General Call Status Bit Clear.
0x0
W
0
Does not clear general call status and general call ID bits.
1
Clear general call status and general call ID bits. The general call status and general call
ID bits are not reset by anything other than a write to this bit or a full reset.
3 HGCEN
Hardware General Call Enable. When this bit and the general call enable bit are set, after
receiving a general call, the device and a data byte check the contents of the ALT register
against the receive shift register. If these registers match, the device has received a hardware
general call. This call is used if a device requires urgent attention from a master device without
knowing which master to which to turn. This is a to whom it may concern call. The device that
requires attention embeds its own address into the message. The LSB of the ALT register must
always be written to a 1, as per the I
2
C January 2000 specification.
0x0 R/W
2 GCEN
General Call Enable. This bit enables the I
2
C slave to acknowledge an I
2
C general call,
Address 0x00 (write).
0x0 R/W