diff --git a/blk/420 b/blk/420
index 57434be..1aad5e6 100644
--- a/blk/420
+++ b/blk/420
@@ -4,7 +4,8 @@ Load range: B423-B436
 
 This subsystem is designed for a ad-hoc adapter card that acts
 as a SPI relay between the z80 bus and the SD card. It requires
-a driver providing the SPI Relay protocol.
+a driver providing the SPI Relay protocol. You need to define
+SDC_DEVID to specify which ID will be supplied to (spie).
 
 Through that layer, this driver implements the SDC protocol
 allowing it to provide BLK@ and BLK!.
diff --git a/blk/429 b/blk/429
index 1b89810..f826569 100644
--- a/blk/429
+++ b/blk/429
@@ -1,15 +1,15 @@
 ( cmd arg1 arg2 -- r )
 ( Send a command that expects a R1 response, handling CS. )
-: SDCMDR1 (spie) _cmd (spid) ;
+: SDCMDR1 [ SDC_DEVID LITN ] (spie) _cmd 0 (spie) ;
 
 ( cmd arg1 arg2 -- r arg1 arg2 )
 ( Send a command that expects a R7 response, handling CS. A R7
   is a R1 followed by 4 bytes. arg1 contains bytes 0:1, arg2
   has 2:3 )
 : SDCMDR7
-    (spie)
+    [ SDC_DEVID LITN ] (spie)
     _cmd                 ( r )
     _idle 8 LSHIFT _idle +  ( r arg1 )
     _idle 8 LSHIFT _idle +  ( r arg1 arg2 )
-    (spid)
+    0 (spie)
 ;
diff --git a/blk/430 b/blk/430
index 8066197..912dc82 100644
--- a/blk/430
+++ b/blk/430
@@ -1,4 +1,4 @@
-: _err (spid) ABORT" SDerr" ;
+: _err 0 (spie) ABORT" SDerr" ;
 
 ( Tight definition ahead, pre-comment.
 
diff --git a/blk/432 b/blk/432
index b5799bf..fb7b9f0 100644
--- a/blk/432
+++ b/blk/432
@@ -1,5 +1,6 @@
 : _sdc@  ( dstaddr blkno -- )
-    (spie) 0x51 ( CMD17 ) 0 ROT ( a cmd 0 blkno ) _cmd
+    [ SDC_DEVID LITN ] (spie)
+    0x51 ( CMD17 ) 0 ROT ( a cmd 0 blkno ) _cmd
     IF _err THEN
     _wait 0xfe = NOT IF _err THEN
     0 SWAP               ( crc a )
@@ -11,5 +12,5 @@
     LOOP
     DROP                 ( crc1 )
     _idle 8 LSHIFT _idle +  ( crc2 )
-    _wait DROP (spid)
+    _wait DROP 0 (spie)
     = NOT IF _err THEN ;
diff --git a/blk/434 b/blk/434
index 6d8aebf..6f74196 100644
--- a/blk/434
+++ b/blk/434
@@ -1,8 +1,8 @@
 : _sdc!  ( srcaddr blkno -- )
-    (spie) 0x58 ( CMD24 ) 0 ROT ( a cmd 0 blkno ) _cmd
+    [ SDC_DEVID LITN ] (spie)
+    0x58 ( CMD24 ) 0 ROT ( a cmd 0 blkno ) _cmd
     IF _err THEN
-    _idle DROP 0xfe (spix) DROP
-    0 SWAP           ( crc a )
+    _idle DROP 0xfe (spix) DROP 0 SWAP ( crc a )
     512 0 DO         ( crc a )
         C@+          ( crc a+1 n )
         ROT OVER     ( a n crc n )
@@ -13,4 +13,4 @@
     LOOP
     DROP ( crc ) 256 /MOD ( lsb msb )
     (spix) DROP (spix) DROP
-    _wait DROP (spid) ;
+    _wait DROP 0 (spie) ;
diff --git a/blk/595 b/blk/595
index 42fcecc..69080af 100644
--- a/blk/595
+++ b/blk/595
@@ -1,15 +1,10 @@
 SPI relay driver
 
 This driver is designed for a ad-hoc adapter card that acts as a
-SPI relay between the z80 bus and the SPI device. Sending any-
-thing on SPI_CSLOW and SPI_CSHIGH is expected to select/deselect
-the device, and writing to SPI_DATA is expected to initiate a
-byte exchange. The result of the exchange is excpected to be re-
-trieved by reading SPI_DATA.
-
-You also need to define the exchange delay with SPI_DELAY. If
-SPI clock is the same as system clock, 2 NOPs are enough:
-
-: SPI_DELAY NOP, NOP, ;
+SPI relay between the z80 bus and the SPI device. When writing
+to SPI_CTL, we expect a bitmask of the device to select, with
+0 meaning that everything is de-selected. Reading SPI_CTL
+returns 0 if the device is ready or 1 if it's still running an
+exchange. Writing to SPI_DATA initiates an exchange.
 
 Provides the SPI relay protocol. Load driver with "596 LOAD".
diff --git a/blk/596 b/blk/596
index e38ff34..e4e2e29 100644
--- a/blk/596
+++ b/blk/596
@@ -1,12 +1,13 @@
 CODE (spix) ( n -- n )
-    HL POP,
-    chkPS,
-    A L LDrr,
+    HL POP, chkPS, A L LDrr,
     SPI_DATA OUTiA,
-    SPI_DELAY
+    ( wait until xchg is done )
+    BEGIN, SPI_CTL INAi, A ORr, JRNZ, AGAIN,
     SPI_DATA INAi,
     L A LDrr,
     HL PUSH,
 ;CODE
-CODE (spie) SPI_CSLOW OUTiA, ;CODE
-CODE (spid) SPI_CSHIGH OUTiA, ;CODE
+CODE (spie) ( n -- )
+    HL POP, chkPS, A L LDrr,
+    SPI_CTL OUTiA,
+;CODE
diff --git a/blk/691 b/blk/691
index 2b618ba..851d921 100644
--- a/blk/691
+++ b/blk/691
@@ -7,8 +7,8 @@ VARIABLE aspprevx
     SWAP aspprevx ! ( b ) ;
 : _cmd ( b4 b3 b2 b1 -- r4 ) _xc DROP _x DROP _xc DROP _x ;
 : asprdy ( -- ) BEGIN 0 0 0 0xf0 _cmd 1 AND NOT UNTIL ;
-: asp$ ( -- )
-    ( RESET pulse ) (spie) (spid) (spie)
+: asp$ ( spidevid -- )
+    ( RESET pulse ) DUP (spie) 0 (spie) (spie)
     ( wait >20ms ) 5000 0 DO LOOP
     ( enable prog ) 0xac (spix) DROP
     0x53 _x DROP 0 _xc DROP 0 _x DROP ;
diff --git a/doc/protocol.txt b/doc/protocol.txt
index c8d2d90..85b06bf 100644
--- a/doc/protocol.txt
+++ b/doc/protocol.txt
@@ -15,13 +15,25 @@ These protocols are described here.
 
 # PS/2 protocol
 
+This protocol enables communication with a device that spits
+PS/2 keycodes.
+
 (ps2kc)   -- kc    Returns the next typed PS/2 keycode from the
                    console. Blocking.
 
 # SPI Relay protocol
 
-(spie)    --       Enable SPI device
-(spid)    --       Disable SPI device
+This protocol enables communication with a SPI relay. This
+protocol is designed to support devices with multiple endpoints.
+To that end, (spie) takes a device ID argument, with a meaning
+that is up to the device itself. To disable all devices, supply
+0 to (spie).
+
+We expect relay devices to support only one enabled device at
+once. Enabling a specific device is expected to disable the
+previously enabled one.
+
+(spie)    n --     Enable SPI device
 (spix)    n -- n   Perform SPI exchange (push a number, get a
                    number back)
                   
diff --git a/emul/hw/rc2014/classic.c b/emul/hw/rc2014/classic.c
index 9d7ba16..c363d60 100644
--- a/emul/hw/rc2014/classic.c
+++ b/emul/hw/rc2014/classic.c
@@ -18,8 +18,7 @@
 #define RAMSTART 0x8000
 #define ACIA_CTL_PORT 0x80
 #define ACIA_DATA_PORT 0x81
-#define SDC_CSHIGH 0x06
-#define SDC_CSLOW 0x05
+#define SDC_CTL 0x05
 #define SDC_SPI 0x04
 #define MAX_ROMSIZE 0x2000
 
@@ -56,14 +55,16 @@ static void iowr_sdc_spi(uint8_t val)
     sdc_spi_wr(&sdc, val);
 }
 
-static void iowr_sdc_cshigh(uint8_t val)
+// in emulation, exchanges are always instantaneous, so we
+// always report as ready.
+static uint8_t iord_sdc_ctl()
 {
-    sdc_cshigh(&sdc);
+    return 0;
 }
 
-static void iowr_sdc_cslow(uint8_t val)
+static void iowr_sdc_ctl(uint8_t val)
 {
-    sdc_cslow(&sdc);
+    sdc_ctl_wr(&sdc, val);
 }
 
 int main(int argc, char *argv[])
@@ -117,8 +118,8 @@ int main(int argc, char *argv[])
     m->iowr[ACIA_DATA_PORT] = iowr_acia_data;
     m->iord[SDC_SPI] = iord_sdc_spi;
     m->iowr[SDC_SPI] = iowr_sdc_spi;
-    m->iowr[SDC_CSHIGH] = iowr_sdc_cshigh;
-    m->iowr[SDC_CSLOW] = iowr_sdc_cslow;
+    m->iord[SDC_CTL] = iord_sdc_ctl;
+    m->iowr[SDC_CTL] = iowr_sdc_ctl;
 
     char tosend = 0;
     while (emul_step()) {
diff --git a/emul/hw/rc2014/sdc.c b/emul/hw/rc2014/sdc.c
index ed39939..6339e0b 100644
--- a/emul/hw/rc2014/sdc.c
+++ b/emul/hw/rc2014/sdc.c
@@ -23,14 +23,12 @@ void sdc_init(SDC *sdc)
     sdc->cmd24bytes = -2;
 }
 
-void sdc_cslow(SDC *sdc)
+// TODO: for now, any nonzero value enables the SDC. To allow
+// emulation of systems with multi-devices SPI relay, change
+// this.
+void sdc_ctl_wr(SDC *sdc, uint8_t val)
 {
-    sdc->selected = true;
-}
-
-void sdc_cshigh(SDC *sdc)
-{
-    sdc->selected = false;
+    sdc->selected = val;
 }
 
 void sdc_spi_wr(SDC *sdc, uint8_t val)
diff --git a/emul/hw/rc2014/sdc.h b/emul/hw/rc2014/sdc.h
index 6a84ecb..7298ad2 100644
--- a/emul/hw/rc2014/sdc.h
+++ b/emul/hw/rc2014/sdc.h
@@ -31,7 +31,6 @@ typedef struct {
 } SDC;
 
 void sdc_init(SDC *sdc);
-void sdc_cslow(SDC *sdc);
-void sdc_cshigh(SDC *sdc);
+void sdc_ctl_wr(SDC *sdc, uint8_t val);
 void sdc_spi_wr(SDC *sdc, uint8_t val);
 uint8_t sdc_spi_rd(SDC *sdc);
diff --git a/recipes/rc2014/sdcard.md b/recipes/rc2014/sdcard.md
index c3332f1..975dbd8 100644
--- a/recipes/rc2014/sdcard.md
+++ b/recipes/rc2014/sdcard.md
@@ -1,5 +1,12 @@
 # Accessing a MicroSD card
 
+Warning: this recipe is temporarily broken. The schema below hasn't yet been
+updated to work with the new SPI relay protocol. If you've already built an
+old design, use an earlier commit or work around it in the SPI driver it should
+only be a matter of testing the input value for zero-ness to decide whether we
+ping the CSLOW or CSHIGH port. If you haven't, wait a little bit before building
+one: the upcoming design is better.
+
 SD cards are great because they are accessible directly. No supporting IC is
 necessary. The easiest way to access them is through the SPI protocol.