UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
167 of 268
NXP Semiconductors
UM10413
MPT612 User manual
18.3.9 Setup and hold time requirements on CS with respect to SK in Microwire
mode
In Microwire mode, the SSP slave samples the first bit of received data on the rising edge
of SK after CS has gone LOW. Masters that drive a free-running SK must ensure that the
CS signal has sufficient setup and hold margins with respect to the rising edge of SK.
illustrates the setup and hold time requirements. With respect to the SK rising
edge on which the first bit of receive data is to be sampled by the SSP slave, CS must
have a setup of at least twice the period of SK on which the SSP operates. With respect to
the SK rising edge previous to this edge, CS must have a hold of at least one SK period.
18.4 Register
description
The SSP contains 9 registers as shown in
. All registers are byte, halfword and
word accessible.
Fig 50. Microwire frame format (continuous transfers)
SK
CS
SO
MSB
LSB
LSB
SI
LSB
0
MSB
4 to 16 bits
output data
4 to 16 bits
output data
8 bit control
aaa-000613
LSB
MSB
Fig 51. Microwire frame format (continuous transfers) - detailed
SK
CS
SI
aaa-000614
t
HOLD
= t
SK
t
SETUP
= 2*t
SK
Table 148. SSP register map
Name
Description
Access
Reset value
Address
SSPCR0
control register 0. Selects serial clock rate,
bus type, and data size.
R/W 0x0000
0xE006 8000
SSPCR1
control register 1. Selects Master/Slave
and other modes.
R/W 0x00
0xE006 8004
SSPDR
data register. Writes fill the transmit FIFO,
and reads empty the receive FIFO.
R/W
0x0000
0xE006 8008