
FPGA Registers
EPU-4562 Programmer’s Reference Manual
12
Table 8: TCR – 8254 Timer Control Register
Bit
Identifier
Access
Default
Description
7
TMR5GATE
R/W
0
Debug/Test Only: Controls the “gate” signal on 8254 timer #5 when not
using an external gate signal:
0 – Gate on signal GCTC5 is disabled
1 – Gate on signal GCTC5 is enabled
Always set to 0 when configuring timer modes except when TMRFULL
is ‘0’ and then it should be set to ‘1’ and not changed unless using
internal clocking.
6
TMR4GATE
R/W
0
Debug/Test Only: Controls the “gate” signal on 8254 timer #4 when not
using an external gate signal:
0 – Gate on signal GCTC4 is disabled
1 – Gate on signal GCTC4 is enabled
Always set to 0 when configuring timer modes except when TMRFULL
is ‘0’ and then it should be set to ‘1’ and not changed unless using
internal clocking
5
TMR3GATE
R/W
0
Debug/Test Only: Controls the “gate” signal on 8254 timer #3 when not
using an external gate signal:
0 – Gate on signal GCTC3 is disabled
1 – Gate on signal GCTC3 is enabled
Always set to 0 when configuring timer modes except when TMRFULL
is ‘0’ and then it should be set to ‘1’ and not changed unless using
internal clocking
4
TM45MODE
R/W
0
Mode to set timers #4 and #5 in:
0 – Timer #4 and #5 form one 32-bit timer controlled by timer #1 signals
1 – Timer #4 and Timer #5 are separate 16-bit timers with their own
control signals.
Almost always used in 32-bit mode especially when TMRFULL is a ‘0’
(the 16-bit timer #5 if of limited use)
3
TM4CLKSEL
R/W
0
Timer #4 Clock Select:
0 – Use internal 4.125 MHz clock (derived from LPC clock)
1 – Use external ICTC4 assigned to digital I/O
Timer #5 is always on internal clock if configured as a 16-bit clock
2
TM3CLKSEL
R/W
0
Timer #3 Clock Select:
0 – Use internal 4.125 MHz clock (derived from LPC clock)
1 – Use external ICTC3 assigned to digital I/O
1
TMROCTST
R/W
0
Debug/Test Only: Used to derive OCTCx outputs with TIMxGATE
signals for continuity testing only:
0 – Normal operation
1 – Drive OCTCx outputs with corresponding TMRxGATE control
registers (for example, OCTC4 with TMR4GATE) for continuity testing.
0
TMRFULL
R/W
0
This bit can be read or written to, but it has no function.