Motorola ColdFire MCF5281 - Manual (Page 260)

Signal Descriptions
14-20 Freescale Semiconductor
14.2.1.6 Transfer Error Acknowledge (TEA)
This signal indicates an error condition exists for the bus transfer. The bus cycle is terminated and the CPU
begins execution of the access error exception. This signal is an input in master mode.
This pin can also be configured as GPIO PE5.
14.2.1.7 Read/Write (R/W)
This output signal indicates the direction of the data transfer on the bus. A logic 1 indicates a read from a
slave device and a logic 0 indicates a write to a slave device.
This pin can also be configured as GPIO PE4.
14.2.1.8 Transfer Size(SIZ[1:0])
When the device is in normal mode, static bus sizing lets the programmer change data bus width between
8, 16, and 32 bits for each chip select. The SIZ[1:0] outputs specify the data access size of the current
external bus reference as shown in
Table 14-6 .
Note that for misaligned transfers, SIZ[1:0] indicate the size of each transfer. For example, if a longword
access occurs at a misaligned offset of 0x1, a byte is transferred first (SIZ[1:0] = 01), a word is next
transferred at offset 0x2 (SIZ[1:0] = 10), then the final byte is transferred at offset 0x4 (SIZ[1:0] = 01).
For aligned transfers larger than the port size, SIZ[1:0] behaves as follows:
• If bursting is used, SIZ[1:0] stays at the size of transfer.
• If bursting is inhibited, SIZ[1:0] first shows the size of the transfer and then shows the port size.
For burst-inhibited transfers, SIZ[1:0] changes with each TS assertion to reflect the next transfer size. For
transfers to port sizes smaller than the transfer size, SIZ[1:0] indicates the size of the entire transfer on the
first access and the size of the current port transfer on subsequent transfers. For example, for a longword
write to an 8-bit port, SIZ[1:0] = 00 for the first byte transfer and 01 for the next three.
These pins can also be configured as GPIO PE[3:2] or SYNCA, SYNCB.
14.2.1.9 Transfer Start (TS)
The device asserts TS during the first CLKOUT cycle of a transfer when address and attributes (TIP, R/W,
and SIZ[1:0]) are valid. TS is negated in the following CLKOUT cycle.
This pin can also be configured as GPIO PE1 or SYNCA.
Table 14-6. Transfer Size Encoding
SIZ[1:0] Transfer Size
00 Longword
01 Byte
10 Word
11 16-byte line
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3