Cirrus Logic EP93xx - Manual (Page 617)

DS785UM1 17-21
Copyright 2007 Cirrus Logic
IrDA
EP93xx User’s Guide
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17.5.4 IrDA Integration Information
17.5.4.1 Enabling Infrared Modes
17.5.4.2 Clocking Requirements
There are four clocks, PCLK, MIRCLK, FIRCLK, and UARTCLK.
Version 1.1 of the Infrared Data Association standard indicates the following:
• FIRCLK must by 48.0 MHz with a tolerance of 0.01%.
• MIRCLK must be 18.432 MHz with a tolerance of 0.1%.
The worst case ratio that can be supported for PCLK:FIRCLK is a ratio of 1:5. The maximum
that PCLK can be is 66 MHz, therefore:
Any frequencies outside the above range are not supported and will result in incorrect
behavior of the FIR mode of the infrared peripheral.
Since MIRCLK is 18.432 MHz, PCLK can be as low as 3.68 MHz and as high as 66 MHz. Any
PCLK frequency in this range is allowable. Any PCLK frequencies outside the range are not
supported and will result in incorrect behavior of the MIR mode of the infrared peripheral,
therefore:
The tolerance of UARTCLK is defined by the UART to which it is connected.
UARTCLK frequency must accommodate the desired range of baud rates:
The frequency of UARTCLK must also be within the required error limits for all baud rates to
be used.
Table 17-5. UART2 / IrDA Modes
Mode
DeviceCfg Register UART2Ctrl Register IrEnable Register
U2EN IonU2 SIREn UARTE EN[1] EN[0]
Disabled 0 x 0 0 0 0
UART2 1 0 0 1 0 0
SIR 1 1 1 1 0 1
MIR x 1 0 0 1 0
FIR x 1 0 0 1 1
1
5
---F
FIRCLK
F
PCLK
66.0MHz
< <
3.68MHz F
PCLK
66.0MHz
≤ ≤
F
UARTCLK
MIN
32 baudrate
MAX
× ≥
F
UARTCLK
MA X
32 65536 b
×
audrate
MIN
Ч ≤