Signal Descriptions
MCF5272 ColdFire Integrated Microprocessor User’s Manual, Rev. 3
19-22
Freescale Semiconductor
19.6.4
Transfer Acknowledge (TA/PB5)
Assertion of the transfer acknowledge (TA/PB5) input terminates an external bus cycle. It is enabled on a
per chip select basis by programming the wait state field to 0x1F in the corresponding chip select option
register (CSORn[WS]). This pin requires a 4.7-K pull-up resistor or external logic that drives inactive
high.
TA must always be returned high before it can be detected again. Asserting TA into the next bus cycle has
no effect and does not terminate the bus cycle.
NOTE:
Even though EBI modes set to SDRAM require setting the wait state field
in the chip select option register to 31, a low signal should never be applied
to TA during such accesses. For SDRAM accesses the bus cycle is
terminated internally by circuitry in the SDRAM module.
19.6.5
Hi-Z
HiZ is a test signal. When it is connected to GND during reset, all output pins are driven to high impedance.
A 4.7-K pullup resistor should be connected to this signal if the Hi-Z function is not used. Hi-Z
configuration input is sampled on the rising edge of Reset Output (RSTO).
19.6.6
Bypass
Bypass is a Freescale test mode signal. This signal should be left unconnected.
19.6.7
SDRAM Row Address Strobe (RAS0)
RAS0 is the SDRAM row address strobe output.
19.6.8
SDRAM Column Address Strobe (CAS0)
CAS0 is the SDRAM column address strobe output.
19.6.9
SDRAM Clock (SDCLK)
The SDRAM clock output (SDCLK) is the same frequency as the CPU clock.
19.6.10 SDRAM Write Enable (SDWE)
This output is the SDRAM write enable.
19.6.11 SDRAM Clock Enable (SDCLKE)
This output is the SDRAM clock enable.