Owner's manual

Table Of Contents
18-2 DS785UM1
Copyright 2007 Cirrus Logic
Timers
EP93xx User’s Guide
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18
18.1.2.1 Free Running Mode
In free running mode, counters TC1 and TC2 will wrap to 0xFFFF when they reach zero
(underflow), and continue counting down. Counter TC3 will wrap to 0xFFFFFFFF when it
underflows, and continues counting down.
18.1.2.2 Pre-load Mode
In pre-load (periodic) mode, the value written to the TC1, TC2 or TC3 Load registers is
automatically re-loaded when the counter underflows. This mode can be used to generate a
programmable periodic interrupt.
18.1.3 40-bit Timer Operation
The time stamp debug timer is a 40-bit up-counter used only for long term debugging (TC4).
Its clock source is the 14.7456 MHz clock, divided by 15 to give a 983.04 kHz reference. The
timer value may be read at any time by reading the lower 32-bit word first and then the high
byte. Dividing the result by 983 yields a timestamp in milliseconds. The debug timer does not
cause an interrupt. The timer is controlled by a single enable bit. When the timer is enabled, it
begins counting from zero and when it is disabled, it is cleared back to zero. When it reaches
its maximum value (0xFF_FFFF_FFFF) it wraps around to zero and continues counting
upwards.
18.2 Registers
Table 18-1. Timers Register Map
Address Read Location Write Location Size Reset Value
0x8081_0000 "Timer1Load," "Timer1Load," 16 bits 0
0x8081_0004 "Timer1Value," - 16 bits 0
0x8081_0008 "Timer1Control," "Timer1Control," 8 bits 0
0x8081_000C Reserved "Timer1Clear," 1 bit -
0x8081_0020 "Timer1Load," "Timer2Load" 16 bits 0
0x8081_0024 "Timer2Value" - 16 bits 0
0x8081_0028 "Timer2Control," "Timer2Control," 8 bits 0
0x8081_002C Reserved "Timer2Clear," 1 bit -
0x8081_0060 "Timer4ValueLow" -320
0x8081_0064
Timer4Enable
a
/ "Timer4ValueHigh"
a. “Enable” is a field in the "Timer4ValueHigh" register.
Timer4Enable 9 0
0x8081_0080 "Timer3Load" "Timer3Load" 32 bits 0
0x8081_0084 "Timer3Value" - 32 bits 0
0x8081_0088 "Timer3Control" "Timer3Load" 32 bits 0
0x8081_008C Reserved "Timer3Clear" 1 bit -
0x8081_0010 Reserved Reserved - -
0x8081_0030 Reserved Reserved - -
0x8081_0040 Reserved Reserved - -
0x8081_0090 Reserved Reserved - -