System Configuration and Control
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To reset a peripheral or group of peripherals, follow these steps:
1. Set COUNT = 08h in PSRCR.
2. Initiate the desired peripheral reset by setting to 1 the bits of PRCR.
3. Do not attempt to access the peripheral for at least the number of clock cycles set in the PSRCR
register. A repeated NOP may be necessary.
In some cases, a single reset is used for multiple peripherals. For example, PG4_RST controls the reset
to the LCD controller, I2S2, I2S3, UART, and SPI.
1.7.5.1
Peripheral Software Reset Counter Register (PSRCR) [1C04h]
The Peripheral Software Reset Counter Register (PSRCR) is shown in
Table 1-58
and described in
Table 1-58
.
Figure 1-46. Peripheral Software Reset Counter Register (PSRCR) [1C04h]
15
0
COUNT
R/W-0
LEGEND: R/W = Read/Write; -n = value after reset
Table 1-58. Peripheral Software Reset Counter Register (PSRCR) Field Descriptions
Bit
Field
Value
Description
15-0
COUNT
0-FFFFh
Count bits. These bits specify the number of system clock (SYSCLK) cycles the software
reset signals are asserted. When the software counter reaches 0, the software reset bits
will be cleared to 0. Always initialize this field with a value of at least 08h.
1.7.5.2
Peripheral Reset Control Register (PRCR) [1C05h]
Writing a 1 to any bits in this register initiates the reset sequence for the associated peripherals. The
associated peripherals will be held in reset for the duration of clock cycles set in the PSRCR register and
they should not be accessed during that time. Reads of this register return the state of the reset signal for
the associated peripherals. In other words, polling may be used to wait for the reset to become
de-asserted.
The Peripheral Reset Control Register (PRCR) is shown in
Figure 1-47
and described in
Table 1-59
.
Figure 1-47. Peripheral Reset Control Register (PRCR) [1C05h]
15
14
13
12
11
10
9
8
Reserved
R-0
7
6
5
4
3
2
1
0
PG4_RST
Reserved
PG3_RST
DMA_RST
USB_RST
SAR_RST
PG1_RST
I2C_RST
R/W-0
R-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 1-59. Peripheral Reset Control Register (PRCR) Field Descriptions
Bit
Field
Value
Description
15-8
Reserved
0
Reserved. Always write 0 to these bits.
7
PG4_RST
Peripheral group 4 software reset bit. Drives the LCD, I2S2, I2S3, UART, and SPI reset signal.
Write 0
Writing zero has no effect
Write 1
Writing one starts resetting the peripheral group
Read 0
Reading zero means that peripheral group is out of reset
Read 1
Reading one means the peripheral group is being held in reset and should not be accessed
6
Reserved
0
Reserved, always write 0 to this bit.
74
System Control
SPRUFX5A – October 2010 – Revised November 2010
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