
MC68CK338
MC68CK338TS/D
MOTOROLA
71
Information to be transmitted must be written to transmit data RAM in a right-justified format. The QSPI
cannot modify information in the transmit data RAM. The QSPI copies the information to its data serial-
izer for transmission. Information remains in transmit RAM until overwritten.
Command RAM is used by the QSPI when in master mode. The CPU writes one byte of control infor-
mation to this segment for each QSPI command to be executed. The QSPI cannot modify information
in command RAM.
Command RAM consists of 16 bytes. Each byte is divided into two fields. The peripheral chip-select
field enables peripherals for transfer. The command control field provides transfer options.
A maximum of 16 commands can be in the queue. Queue execution by the QSPI proceeds from the
address in NEWQP[3:0] through the address in ENDQP[3:0]. (Both of these fields are in SPCR2).
CONT — Continue
0 = Control of chip selects returned to PORTQS after transfer is complete.
1 = Peripheral chip selects remain asserted after transfer is complete.
BITSE — Bits per Transfer Enable
0 = 8 bits
1 = Number of bits set in BITS[3:0] field of SPCR0
DT — Delay after Transfer
The QSPI provides a variable delay at the end of serial transfer to facilitate the interface with peripherals
that have a latency requirement. The delay between transfers is determined by the SPCR1 DTL[6:0]
field.
DSCK — PCS to SCK Delay
0 = PCS valid to SCK transition is one-half SCK.
1 = SPCR1 DSCKL[6:0] field specifies delay from PCS valid to SCK.
PCS[3:0] — Peripheral Chip Select
Use peripheral chip-select bits to select an external device for serial data transfer. More than one pe-
ripheral chip select can be activated at a time, and more than one peripheral chip can be connected to
each PCS pin, provided that proper fanout is observed.
NOTES:
1.
The PCS0 bit represents the dual-function PCS0/SS
.
CR[0:F] —
Command RAM
$YFFD40
7
6
5
4
3
2
1
0
CONT
BITSE
DT
DSCK
PCS3
PCS2
PCS1
PCS0
1
–
–
–
–
–
–
–
–
CONT
BITSE
DT
DSCK
PCS3
PCS2
PCS1
PCS0
1
COMMAND CONTROL
PERIPHERAL CHIP SELECT